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^ m i* -■'-'

TOOL-MAKING

A PRACTICAL TREATISE ON THE ART OF MAKING

TOOLS, JIGS, AND FIXTURES, WITH HELPFUL

SUGGESTIONS ON HEAT TREATMENT

OF CARBON AND HIGH-SPEED

STEELS FOR TOOLS,

PUNCHES, AND

DIES

By EDWARD R. MARKHAM

IN8TRUCTOB IN SHOP WORK, HARVARD UNIVERSITY AND

RINDGE TECHNICAL SCHOOL

CONSULTING EXPERT IN HEAT TREATMENT OF STEEL

kuRMERLY SUPERINTENDENT, WALTHAM WATCH TOOL COMPANY

AMERICAN SOCIETY OF MECHANICAL ENGINEERS

ILLUSTRATED

AMERICAN TECHNICAL SOCIETY

CHICAGO

1919

HARVARD UNIVERSITY

DIVISION or tD*-'-''^ -••

■URBAU OP VOCATIONAU uu.UANt*

lo il <

HARVARD C0LLE6E LIL
1»AWFEIWED FROM THZ
LIBRARY OF THE
GRADUATE SCHOOL OF EDUCATIOJ*

AMERICAN TECHNICAL SOCIETY

COPYRIGHTBD IN GREAT ^RITAIN
ALL RIGHTS RBSBRVED

INTRODUCTION

T^HE history of the development of the tool-making art is, of
course, the history of the mechanical development of the
country. The hand working tools came first and then with the
invention of each' successive machine came the creation of tools
to go with it. The gradual evolution of machine methods
brought an increase in the required accuracy of workmanship
and this in turn demanded more precise methods and greater
skill on the part of the tool maker. Today, therefore, the large
body of so-called "tool makers" represents the most skilled,
the most inventive, and the most intelligent of the army of
V mechanics which forms the back bone of our immense mechanical
industries.

^ Many phases of this mechanical development have increased
the importance of the tool maker — the introduction of high-
speed steels, demanding greater skill in construction of the tools
because of the greater demands upon them; the variation of
hardening and tempering methods owing to the variety of steels
used; and particularly the use of "production" methods which
necessitates the design and manufacture of complicated tools,
jigs, and fixtures for the rapid duplication of any given machine.
The design of efficient and complete sets of such tools requires
highly developed knowledge of machine methods, and a thorough
understanding of the machines for which the tools are designed.

^ The author of this work has had years of experience not only in
teaching the subject but in the practical side as well, and is able
to give the reader a multitude of helpful suggestions for success-
fully carrying out the mechanical operations required. It is the
hope of the publishers that this work will be found a worthy
contribution to our standard technical literature.

CONTENTS

PAGE

Tool-maker and his equipment 1

Fundamental requirements for successful work 1

Necessary tools 4

Tool materials and their treatment 8

Cast iron 8

Wrought iron 8

Machine steel ". 8

Converted steel 9

Crucible steel and its preparation 10

Use of pyrometers 15

Hardening and tempering crucible steel 19

Alloy steels 27

Modem high-speed steels 28

STANDARD TOOLS

DriUs 32

Flat drills 32

Single-lip drill 35

Twist drills 38

Reamers 45

Straight reamers 45

Fluted hand reamers 46

Taper reamers 59

Formed reamers 60

Arbors 63

Tool-steel mandrels 63

Expanding mandrels 67

Eccentric arbors 69

MiUing-machine arbors 71

Taps 73

Process of making 73

Hand taps 76

Machine taps 80

Taper taps 81

Threads 86

Tap wrenches 89

Tap holders 90

CONTENTS

PAGE

Thread-cutting dies 93

Solid type 93

Adjustable type 96

Counterbores 103

Twoedged flat counterbores 103

Counterbores with f om* cutting edges 104

Counterbores for large work 107

Counterbores with inserted pilots 109

Hollow mills 114

Plain and adjustable hollow mills 114

Hollow mills with inserted blades 117

Hollow mills with pilot 1 18

Forming tools 119

Flat forming tools 119

Screw-machine forming tools 121

Tool holders 124

Milling cutters 126

Use of high-speed steel 126

Solid straight cutters 127

Side milling cutter 132

Spiral milling cutters 134

MiUing cutters with inserted teeth 139

Formed cutters 143

End mills 152

Milling machine fixtures 158

Milhng machine vises. .^ 160

Special holders 163

Holders for vertical milling ^iiachines , . 164

Drill jigs 164

Simple slab jig 166

Locating holes for bushings 168

Boring bushing holes on milling machines 173

Jig types 179

Bushings ^ 186

Punch and die work 193

Dies 193

Making die 196

Punches 206

CONTENTS

Punch and die work (continued) page

Gang dies 213

Multiple die 217

Bending die 218

Forming die 221

Hardening drawing and redrawing dies 223

Reversed die 224

Compound dies 225

Triple dies 225

Follow dies 226

Curling dies 228

Wiring dies 229

Compound punching and bending dies 230

Progressive dies 231

Sub-press dies 234

Use of high-speed steel for dies 236

Fluid dies 237

Hollow punches 238

Broaches. . . . *. 241

Design of draw-broaching machines 242

Illustrations of broaching 244

Stock for broaches 247

Making draw broaches 248

Long broach vs. short broach • 252

Push broaches ^53

Keyseating machine 253

Drop-forging dies 254

Drop-forging process 255

Making drop-forging dies 257

Hobbing drop-forging dies 261

Cold-striking dies 262

Gages 263

General directions for making gages 263

Types of gages 265

Draw-in chucks 286

Directions for making ■ • • . 286

TCX)L-MAKING

PARTI

INTRODUCTION
THE TOOUMAKER AND HIS EQUIPMENT

As generally understood, a tool-maker b a machinist who has a
greater knowledge of the trade than is sufficient simply to enable him
to make such miachines or parts of machines as may be the regular
product of the shop in which he is employed.

The business of the tool-maker is to make the tools for producing
the different parts of machines, implements, or apparatus. It
includes the making not only of cutting tools, but also of jigs and
fixtures for holding the work while the various operations are being
done, and the necessary gages to determine when the different parts
are of correct size and shape. It also includes the making of the
models for the different fixtures and gages. In some shops where
there is work enough on the gages and models, the tool-makers regu-
larly employed on this latter work are termed gage-^makers and viodeU
makers, respectively; yet, in the average shop, it is the tool-maker
who makes.these tools and such special machinery as may be required.

Fundamental Requirements for Successful Work. Accuraq^ in
Vital Measurements. In order to acquire any degree of success, the
tool-maker miist have not only the ability to work accurately and
within reasonable time, but also a knowledge of drafting to enable
him ta read quickly and exactly any ordinary drawing. Unless
he can read decimal fractions readily and correctly, he will experience
much difficulty when working to measurements that require accu-
racy to within .0001 inch. As most of the measuring instrmnents
used by the tool-maker read to .001 inch, and some of them to .0001
inch, or even closer, it will be readily seen that in laying off measure-
ments for gages, models, drill jigs, and similar work, a thorough
knowledge of arithmetic is essential.

A tool-maker should be familiar with the accurate reading of the
micrometer and of the vernier, as applied tp the vernier caliper^

3 TOOI^MAKINa

veraier depth gage, and vemier height gage. He must bear in
mind, when uung the vernier caliper for inside measurements, that
it is xitcttauy to add the amount of space occupied by the caliper
pointa AA, Fig. 1, to the apparent reading on the vernier aide.

When measurmg the distance between tlie centers of two holes,
as in Fig. 2, set the veraier so that the portions of the jaw marked
AA, Fig. 1, will exactly caliper the dbtance from £ to £ in Fig. 2.
To the apparent reading of the vernier, add the space occupied by
the csKper points; and from this subtract one-half the diameter of

CmmoTHoI™ by Vm

h hole.

each of the holes. It is necessary to caliper the si

Do not take anything for granted when accurate it

necessary. A reamer ought always to cut an exact size, but experi-

ence proves that it does not invariably do so. If the size of tJie

hole is taken for granted and a mistake of .002 inch is made, an error

of JOOl inch m a m«asweownt would result

TOOL-MAKING 3

JudgmerU in Approximate Measurements. While extreme care
should be exercised when accuracy b essential, there are parts of a
tool where approximate measurements will do. If within i^ inch
is suflSciently exact, it is folly to spend time to get a dimension
within a limit of .0001 inch.

Approximate measurements are those made with the aid of
calipers, dividers, surface gage, etc., set to an ordinary steel rule.
Precise measurements are obtained by the aid of the various meas-
uring instruments graduated to read to very small fractions of an
inch; also by the use of standard reference discs, and standard test
bars, accurate within a limit variation of isjfivv part of an inch. In
using the micrometer, the vernier, or any of the measuring instru-
ments supposed to give accurate readings, it is necessary to exercise
great care in settmg the tools. In setting the vernier, it is well to
use a powerful eyeglass in order that any error in setting may be so
magnified as to be readily
apparent.

The difference
tween the two characters
of measurements de-
scribed — approximate
and precise — may be
readily seen in the plug gage shown in Fig. 3. The gage end A , when
ground and lapped, must be exactly 1 inch in diameter, as shown by
the stamped size on the handle C The handle should be H inch in
diameter and knurled, and the neck, { inch. While the end marked
A is necessarily a precise measurement, B and C are approximate, and
an error of ih inch or more on either diameter would not interfere
with the accuracy of the gage. This does not mean that so great an
amount of variation from given sizes should ever occur; but the
illustration is given to show that the practical workman will never
spend an unnecessary amount of time to produce accurate measure-
ments, when an approximate measurement will do. On the other
hand, all care possible should be taken when lapping the gage end
A to size.

Constant Care of Machines. The working parts of any machine
that may be running should be kept as clean as possible. Do not
allow chips to collect on the shears, V's, of your lathe* If the shears

Fig. 3. Plug Gage

TOOI/-MAKING

become roughed or worn, accurate turning cannot be done. Keep
the machine thoroughly oiled; dean the oil holes out occasionally
with a piece of wire, in order that the oil may get to the bearings.
Be sure the centers of your lathe are in good condition; have them to
gage; and make certain that the live center runs true before taking
any finishing cuts. Try the center gage on your counter^nk occa*
sionally to see that it maintains its correct shape. Keep the center
punch ground to a good pomt. It is advisable to grind the prick
punch used in locating working points in some form of a grinder

having a chuck or collet to hold
the punch while revolving it
against the emery wheel; if the
point is not perfectly round, it
will be impossible to indicate a
piece of work perfectly on the
faceplate of the lathe with the
center indicator.

Necessary Tools. A temier
height gage. Fig. 4, is very use-
ful for making drill jigs, templets,
and other tools requiring very
accurate measurements, and for
locating working points, holes,
or drill bushings. It is used for
obtaining the height of projec-
tions from a plane surface, or the
location of bushings in drill jigs,
etc. The fixed jaw A is of sufiicient thickness to allow the gage to
stand upright. An extension C attached to the movable jaw B can
be used for scribing lines when lading off measurements. In the
absence of a height gage, the regular vernier caliper may be made
to answer the same purpose by making a base which may be
attached to the fixed jaw. Fig. 5.

A small angle iron, having a slot in the upright face to receive a
scale for use in connection with a surface gage when laying off meas-
urements is shown in Fig. 6. The slot should be planed perfectly
square with the base of the angle iron.

A pair of accurately machined M-hloch is a necessary part of

Fig 4 Vrrnier Height Gkge

TOOL-MAKING S

tvay todsnaker'a kit. It made of madiine or tool steel, tbey will

not need truiiig so c^tea as if made of caat

iron. After roughing out the Vs, every sur-

fsco should be pinned square. They should

then be clamped, by means of finger pieces,

against the rail on the planer table, the edge

of the rail having been previously trued. The

bead of the planer should then be set to the

proper angle, usuaUy 45 degrees, and one of

the angles finished; the head may now be set

over the ^posite way and the other angle

faceplaned. The tool used should be ground

to give a smooth cut, as it is not advisable to

do any finishing with a file or scraper.

A few small gage» of the most common
angles wiU be found very convenient, as they
can be used in pieces not accessible to the ordi-
nary bevel protractor; the angles most com-
monly used are 60 degrees, 65 degrees, 70
degiees, and SO degrees. The form of gage is
shown in Fig. 7. If the tool-maker should be
called on to make punch press dies, one or
more angle gages, as shown in Fig. 8, will be AtiSfcaio^ScSUr
found very useful.

Many die-makers use an adjustable square having a narrow

blade which passes through the aperture in the die. The amoimt ol
clearance given is determined by the judgment of the workman

TOOL-MAKING

60*

Fig. 7.

Angie Gac«

Ov'DoglM

While this method does very well when practiced by an experienced
man, it is rather uncertain when attempted by the novice. To get

the proper clearance, the beginner should use
the gage shown in Fig. 8, called, improperly, a die-
maker's square. The angle depends on the nature
of the stock to be punched and on the custom in
the mdividual shop; but a set of three gages, one
91 degrees, one 91) degrees, and one 92 degrees,
will meet the requirements, as the clearance is
seldom less than 1 degree or more than 2 degrees.
The angle should be stamped on the wide part
of the gage, as shown in Fig. 7. To avoid spring-
ing out of shape, the stamping should be done before the gage is
finish-filed at any point.

The tool-maker should always have
at hand a solution of blue tiiriol for col-
oring the surface on which he is to draw
lines. To make the solution, dissolve in
a two-ounce bottle of water all the blue
vitriol crystals the water will take up; to
this add one-half teaspoonf ul of sulphuric
acid< This produces a copper-colored
surface when put on polished steel free from grease and dirt.

Fig. 8. Die-Maker's Square

Fig. 9. Forma of Straightedge aad Holder for Griodiag

A straightedge is a necessary part of a tool-maker's kit. Many
tool«makers have several, varying in length from 1 inch to 12 inches.

TOOL-MAKING 7

or even longer. The tool should be kept in a case in order that its
edge may not become marred. For short stnughtedges, the form
shown at ^ in Fig. 9 is very salisfactofy; this b known as a knifc'edge
straighUdge, For the shorter lengths, pieces of sword blade answer
very well, or steel of the desired form may be procured. Often the
longer lengths are made from steel rectangular in shape, one edge
being planed or milled, as shown at B.

When grinding a straightedge, it is necessary to hold the piece
in such a way as to prevent any spring. Thb may be done by
centering a, piece of brass pr machinery steel, and then milling or
planing a groove, as shown at C, The blade may be held in the
groove by dropping a little soft solder at each end of the blade; if the
blade b more than two inches in length, a drop should be placed at
distances about one inch apart. As straightedges are usually
inclined somewhat in use, it b necessary to grind not only the edge,
but the portions marked e at B. The edge and the cwners should
be lapped by hand by placing fine emery on a flat bench lap. It
will be necessary to finish by oil-stoning any high places that are not
removiMi by lapping. To test the straightedge, try it on a master
straightedge, or on a true surface plate.

Short straightedges for general use should be hardened to pre-
vent excessive wear and also to prevent the edge from becoming
bruised. To harden pieces of thb character successfully, damp
pieces of iron to the sides so that f Irom one-eighth to one^quarter
inch projects. Then heat to a low red. If the edge b thin, harden
in cottonseed oil, plunging the tool beneath the surface of the oil,
and working it up and- down and around in the x)il. If the stock b
too thick to harden in oil, use lukewarm water. If a little cyanide
of potassium b placed on the edge just before dipping, uniform
results will follow.

Master straightedges, 12 inches or more in length, are generally
made from steel that b rectangular in cross-section, with the working
edge left the full thickness of the stock. The edge b ground in a
surface grinder, the tool being held in such a way as to do away
with any liability to spring. A very satisfactory holding device b
the magnetic chuck which precludes all danger of marring the piece.
Long master straightedges are usually made from cast iron and are
heavily ribbed to prevent springing.

8 TOOL-MAKING

TOOL MATERIALS AND THEIR TREATMENT

Cast Iron. On account of its low cost, cast iron is especially
adapted for certain parts of machines and tools. A pattern may be
made and a casting of the desired shape and size produced on short
notice. As cast iron is a weak, brittle metal, it is not employed for
parts that are to be subjt^cted to great strain, unless sufficient metal
can be provided to insure necessary strength. At times when a
large body of metal cannot be used, the necessary strength may be
obtained by constructing ribs to brace the weak portions.

If properly designed, milling machine fiictures, drill jigs, and
various other forms of devices used in holding work to be machined,
or in holding cutting tools, may be made from cast iron.

Wrought Iron. This metal is but little used in the ordinary
machine shop. The low grades of steel, generally known as machine
steel, have in a great measure superseded wrought iron. They are
stronger, are more easily worked in machining operations, and the
first cost is lower than that of good wrought iron.

On account of its fibrous structure, wrought iron does not
weaken so readily as steel, under intermittent strain, shock, or blow,
and it is more satisfactory under such conditions.

Machine SteeL The ordinary low grades of steel are made by
two entirely different processes; and the product of either process,
when used in machine construction, or for such work as is generally
done in the machine shop, is commonly known as machine steel.
As the product of either process may be varied to meet the needs
of the buyer, it b apparent that the term machine steel means little,
covering as it does every form of iron between wrought iron and tool
steel. In order that one may understand the quality of a particular
steel, it is necessary to state the percentage of the various elements
used in its composition.

The two processes employed in making low-grade steels are the
Bessemer process and the open-hearth process. Steel made by the
Bessemer process b known as Bessemer steel, and is made in a
vessel known as a Bessemer converter.

Open-hearth steel, a product of the open-hearth furnace, b
more costly than Bessemer steel, and b also more reliable. The
process being much slower than the Bessemer process, the product
b more under the control of the furnace man.

TOOL-MAKING 9

Steel made by either process may be given any desired per-
centage of oarbon; and as carbon is the element in steel that causes
it to harden when heated red hot and dipped in water, it is apparent
that dead soft steel containing so little carbon that it will not harden,
or steel containing a sufBcient amount to cause it to harden dead
hard, may be produced at the will of the furnace man. Such steel,
even though it contains sufficient carbon to cause it to harden as
much as tool steel, is not strong enough to stand up under the peculiar
strain to which most cutting tools are subjected.

While for certain forms of cutting tools a good grade of high-
carbon open-hearth steel answers very well, its use is not to be advo-
cated except where those in charge are sufficiently versed in the
nature and peculiarities of the metal to know that it will be satis-
factory;

Converted Steel. This metal is many times spoken of as
cfmenled steel, and the process used in its production, as the cementor
tion process. It is made by packing bars of wrought iron in a recep-
tacle made from some refractory material, the bars being surrounded
by charcoal. The cover of the box is sealed, or cemented, with fire
clay to prevent the carbon escaping, this operation giving the
process its name. The carbon given off by the charcoal is absorbed
by the iron, the process being continued until the carbon pene-
trates to the center of the bars; In the process under consid-
eration, the boxes are placed in a furnace, heated to a yellow
heat, and kept at this temperature until the iron is saturated with
carbon. Carbon penetrates iron at the rate of } inch in 24 hours.
Bars } inch thick would require an exposure to the carbon for three
days (72 hours).

As the steel comes from the furnace, the surface is covered with
blisters; hence the product is sometimes called blister steeL These
bars were laid on one another in piles and the piles were heated to a
welding heat, hammered, and welded together into a bar which was
called shear steel. In case shear steel was cut or broken to short
lengths, piled, and welded, the product was called dovble-^hear steel.
Shear steel was the tool steel of commerce.

Formerly, cast iron, wrought iron, and converted steel were the
three forms of iron used in machine construction and in the manu*^
facture of cutting toob.

10 TCM3L-MAKING *

Crucible Steel. Wrought iron contains considerable slag, which
occurs in lines, kno^n as slag lines, running lengthwise of the bar.
These slag lines were present in shear steel, and they were a source
of annoyance when they occurred at the cutting edge of a tool! It
was an English dockmaker, Benjamin Huntsman by name, who
first devised a means to obviate thb difficulty after experiencing
con»derable trouble with clock springs made from converted steel.
It occurred to him that by melting the steel he might be able to get
rid of the slag, as that, being lighter than the steel, would float on
the surface of the melted metal. He broke blister, steel into small
pieces and melted it in a crucible. After the slag was removed the
metal was cast into a block called an ingol. The ingot was ham-
mered but into a bar called crvcible steel.

While Hunstman thus founded the crucible steel industry, he
met with many serious obstacles which have since been overcome by
chemists and steel-mill men; and today, steel, far superior in purity,
strength, and general adaptability, to any that has ever been made,
b produced by the crucible process.

As the product of the crucible was cast in a mold, the metal was
called east steel. As the product of the more recently discovered
processes — ^the Bessemer and the open-hearth — b also cast in molds,
unscrupulous makers sometimes stamp their product "cast steel'',
for the purpose of deceiving the buying public, and good grades of
open-hearth steel, which are high in carbon, are sold as "cast steel".
As previously stated, such steel may answer for certain purposes, yet
for general use a good grade of crucible steel should, as a rule, be
used for cutting tools.

Such steel generally proves to be cheaper than cheap grades^
even though the first cost may be three or four times that of the
cheaper article. Frequently, many dollars' worth of labor b
expended on a few cents' worth of steel; and if a poor steel b used,
the money expended for labor and sted b thrown away.

In the shop where all steel b tested in the chemical laboratory,
it b possible to select stock which contains low percentages of harm-
ful impurities, and whose carbon content i^ high for many classes
of tools. If, however, the percentage of phosphorus b high, such
sted b we(Uc, as the effect of phosphorus b to jnake steel "cold
short", that is, to make It weak when cold.

TOOL-MAKING 11

The quality of steel does not necessarily vary much with the
price, and some of the very costly steels are, for many purposes, no
better than others costing less. It is always advisable to test the
steels, select the ones best adapted to the needs, and pay the price.

Preparation of Crucible Tool Steel

Selection of Stock. Tool steel Is used for tools intended for
cutting, pressing, or working metals or other hard materials to sh^ape.
In order to work tool steel successfully, a knowledge of some of its
peculiarities is necessary.

AUowa7ice for Decarbonization, Carbon is the element in tool
steel that makes it possible to harden it by heating to a red heat and
plunging it into a cooling bath. A bar of steel from the rolling mill
or forge shop is decarbonized on its outer surface, to a considerable
depth; consequently this portion may not harden and if it does, the
results are far from satisfactory. For this reason, if a tool is to be
made having cutting teeth on its outer surface, it is i^ecessary to
select stock of somewhat greater diameter than the finish size, so
that this decarbonized portion may be removed. About A inch
additional for sizes up to } inch, i inch for sizes up to 1} inches,
^ inch for sizes up to 2 inches, and } inch for sizes above 2 inches,
will usually be sufficient.

Various Forms. Tool steel may be procured in almost any
form or quality. It is ordinarily furnished in round, octagonal,
square, or flat bars. Many tool-makers prefer octagonal ateel for
tools which are to be circular in shape, but experience shows that
steel of various shapes of the same make does not vary materially,
provided the quality and temper are the same.

High-Carbon and Low-Carbon SteeL Cutting tools should be
made of high-carbon steel if the metal is to be forged or hardened
by skilful operators. If the steel is to be heated by an inexperienced
man, it is not safe to select a steel having a high percentage of carbon.
For non-cutting tools, such as mandrels, a low-carbon steel is better
— one per cent carbon or less — because with this steel there is not so
great a tendency to spring when hardening.

Hammered SteeL Hammered steel b prized more highly than
rolled steel by many fine tool-makers, but authorities do not agre(
on this point. It is generally conceded, however, that the best toob

12 TOOL-MAKING

can be made from forgings if the heating and hammering have been
correctly done. The steel should be heated uniformly throughout,
and hammered carefully, with heavy blows at first. Lighter blows
should follow, and, when the piece passes from low red to black,
great care is needed to avoid crushing the grain. Steel properly
heated and hammered has a close, fine grain.

Cutting from Bar. It b advisable, when cutting a piece of stock
from a steel bar, to use a cutting tool of some description, such as a
saw or cutting-off tool. It is decidedly poor practice to weaken the
bar with a cold chisel and then to break it by a sudden blow. This
process so disarranges the particles of steel that they do not assume
their proper relations with one another when hardened. If it is
necessary to cut the steel with a chisel, it is best to heat the bar to
a red heat, as in this condition the steel may be cut off without
injury.

Centering. When centering, care should be taken that the
center-punch mark is exactly in the center of the piece on each end,

Fig. 10. Effect of Proper Centering Fig. 11 Effect of Improper Centering

SO that an equal amount of the decarbonized material will be turned
from all parts of the piece, Fig. 10. If centered as shown in Fig. 11,
the decarbonized portion will be entirely removed on the side marked
B, and will not be removed on the side marked A; consequently,
when the piece is hardened, the side marked B will be hard, while the
opposite side A will be soft, or at least not so hard as B.

Straightening. A piece of tool steel that is to be hardened
should never be straightened when cold as it is almost sure to spring
when hardened. If it is bent too much to remove all the decar-
bonized steel when turning to size, it is best, generally speaking, to
take another piece of stock. But if the bent piece must be used,
heat it to a red heat and straighten.

TOOL-MAKING

Annealins* In order that it may be soft enough to work easily,
tool sted must be annealed. The process consists in heating the
metal to a uniform red heat and allowing it to cool slowly. Steel
can generally be bought annealed more cheaply than it can be
annealed when needed in the factory.

Annealing removes the strains, or the tendency of the steel to
crack and spring when hardened. Strains are caused by rolling and
hammering in the 'steel mill or forge shop. In order to remove the
tendency to spring, the piece of steel should be machined somewhere
near to size, sufficient stock being left to machine all over after the
annealing. If the piece is to have a hole in it, such as a milling
machine cutter blank, the hole should be drilled somewhat smaller
than finish size — I'^-inch is the amount generally allowed — ^and the
piece turned in a lathe to remove -all the outer surface which contains
the marks of the hanmier or
rolls. The piece is now ready
for annealing, which may
be done in one of several

ways.

*-T9st Wirea

Fig. 12. Diagram Showing Method of
Annealing Tool Steel

Box Annealing wiih Chat'
coal. For this method, it is
necessary to have a furnace large enough to hold an iron box
of a size sufficient to take the piece to be annealed. To
do the work cheaply, enough pieces should be annealed at a
time to fill one or more boxes, according to the capacity of the
furnace..

The material used in packing the box is wood charcoal, which
should be ground or pounded until the particles are about the size
of a pea. A layer of charcoal covering the bottom to a depth of 1
inch is first placed in the box, then a layer of steel. The different
pieces of steel should not come within } inch of each other, nor
within 1 inch of the box at any point. The spaces between the
pieces are filled with the charcoal, and they are covered to a depth
of 1 inch. Another layer of steel may be put in, if the box is of
sufficient size. When within 1) inches of the top, the remaining
space is filled with charcoal, the whole tamped down, the cover put
on, and the edges luted around with fire clay to prevent the direct
heat of the fire entering the box.

14 TOOL-MAKING

There should be several }-inch holes drilled through the cover
near the center, and through each of those, a piece of A -inch wire
should be placed, as shown in Fig. 12. The wires should extend to
the bottom of the box and project about 1 inch above the top of the
cover, so that they may be readily grasped by the tongs. These
wires are to be drawn from the box and tested in order to determine
the temperature of the contents. The box should be placed in the
furnace, and after it has becpme thoroughly heated, one of the wires
b drawn out by means of a pair of long tongs. If no such tongs are
available, the legs of ordinary tongs may be lengthened by pieces
of gas pipe. If the wire is not red hot, the heating process should
be continued for 10 or 15 minutes longer. Then another wire is
drawn, and the process kept up until a wire id drawn that Is red the
entire length. The work should be timed from the moment the box
is heated through; this is shown by the wire.

The heat should be maintained a sufficient length of time to
insure a uniform heat, which should not be allowed to go above a
full red. The length of time the pieces remain in the fire depends
sontewhat on the size; for steel 2 inches or less in diameter, one hour
after the box is heated through will do; larger pieces require a little
longer time. After running for the necessary length of time, the
heat should be shut off, and the boxes allowed to cool slowly; the
pieces should be left in the box until cold.

This method of annealing gives satisfactory results with large
pieces to be used for certain purposes, but for light, thin materials^
its use is' not advised^ as the steel remains red hot for too long a
period. When articles of this description are annealed, they should
be heated to a low red, then placed in an iron box having two or
three inches of hot ashes in the bottom, the hot ashes being used to
prevent chilling.

Box Armealmg tnik Ashes or Lifme. When there are no facilities
for annealing by the method above described, the steel may be heated
to a uniform red and placed on a piece of board in an iron box, there
being one or two inches of ashes under the board. A second piece of
board should be placed on the steel and the box filled with ashes.
The pieces of wood will smolder and keep the steel hot for a long time.

Another Common method of annealing tool steel is to heat the
piece to a red heat and bury it in ashes or lime. To secure satid-

TOOL-MAKING 15

factory results the ashes or lime should also be heated, which can
be accomplished by first heating a large piece of iron and then bury-
ing it in the contents of the annealing box. When the steel to be
annealed is sufficiently heated, the piece of iron may be removed and
the piece to be annealed put in its place, and thoroughly buried in
order that it may take a long time in cooling. It should be allowed
to remain in the ashes or lime until cold.

W<iter AnneaMng» There is another method of annealing prac-
ticed in some shops, Idiown as the water anneal, which answers in
an emergency, but is not Recommended for general use. The pi^ce
of steel is heated to a low red, making sure that the heat b uniform
throughout^ It should be removed from the fire and held in the
air where no draft can strike it until not a trace of red can be seen
when the piece is held in a dark place. It should then be plunged in
water and allowed to remain until cold. Better results may be
obtained if it is plunged in soapy water or oil.

Strengthening Steel by Annealing. In a previous paragraph it
was stated that there are reasons for annealing steel other than to
soften it. It may be necessary to impart some quality that can
be given only by annealing; it may be necessary to toughen and
strengthen a spindle or other piece, and at the same time, to have it
workable. Use of the following method will secure such results.

The steel is heated red hot and plunged into oil where it is
allowed to remain until cool; it is then heated again to a low red,
removed from the fire, and allowed to cool in the air where no draft
can strike it, and where no moisture can come in contact with it.

Steel annealed by this method is very tough, yet it can be bent
to a greater degree than if annealed by any of the other methods/

Hardening. Tool steel may be hardened by heating to a low
' red heat and plunging in some cooling medium, as water, brine, or oil.

Use of Pyrometers. Nece^aiiy for Accurate Temperature Read-
ings, At the present time, when so much attention is given to
obtaining -exact temperatures in the various processes of heat-treat-
ing steel some form of temperature gage is absolutely essential.
The gage used for determining high temperatures is called a
pyrometer.

A good pyrometer Is a necessity, if the heating of steel is
entrusted to a man who has not had a wide experience in gaging

16 TOOL-MAKING

temperatures with the eye. It is also a great aid to the skilled man,
as furnace conditions vary. Changing degrees of light in the hard-
ening room may deceive even the most experienced hardener; a
man's physical condition may affect his vision; or any one of a
dozen things may cause him to heat steel to a temperature that will
not produce the best re-
sults possible.

In a hardening room
having several furnaces, it
is not alVvays necessary to
provide a pynimeter for
each furnace, as a number
of furnaces can be con-
nected with one instru-
ment so that by moving a
switch each furnace is con-
netted in turn and its tem-
perature can be read from -
the indicator.

As so much depends
on the accuracy of the gage
used in temperature read-
ings, it is always best to
have one that is known
generally as a reliable in-
strument. The extremely
high temperatures to
^,";»,SS°4lS?rrM;.SF^uS^" which the fire ends of
'^""Wi^^^^c^^'""''' ^'^^^ S^S** ^"^ subjected,

makes it necessary to
watch very closely even, the most satisfactory makes, for an
instrument of this kind, unless fairly accurate, is worse than none.
When using a pyrometer for gaging heats, the fire end should
be located as nearly as possible at the same height as the work being
heated in the furnace. The temperature in a furnace varies many
times; that is, it may be much higher 18 inches above the floor of
the furnace than it is at the floor level, and if the work rested on the
bottom and was hut 2 or 3 inches m height, and the fire end of the

TOOL-MAKING 17

gage was located 18 or 20 inches above the. work, the readings might
not accurately indicate the temperature to which the piece was
heated.

Clai/ Cones. In order to malce sure that the instrument is record-
ing correctly, it is a gooil plan to check it occasionally with one ot
known accuracy; or, in the absence of a second gage, it may be
checked by means of clay temperature determining cones, called by
some sentinel pyrometers. The cone should be located as nearly as
pos^ble at the same height as the fire end of the pyrometer. When
making the test, have t!ie furnace at a temperature somewhat lower
than the fusing point of the cone, gradually raising the temperature
until the cone fuses. Notice at the fusing time the reading of the

pyrometer; if the rea'ding agrees with the predetermined fusmg point
ot the cone, it is reasonably certain that the other readings ot the
gage are correct. Some hardeners, however, insbt on testing at
several different temperatures, say at 1350° F., 1850° F., and
2250° F., asserting that if the three readings are correct they know
the gage 13 absolutely reliable at the time at any temperature.'

The cones are convenient also where there is no pyrometer, as
high temperatures may be accurately gaged by their use. Clay
cones are cheap, reliable, and easily obtainable in a large range of
temperature determinations. Each cone has marked on it its
fusing point, so that there is absolutely no need ot error in its use.

Various Types. There are a number of satisfactory makes of
pyrometers on the market, any one ot which, will show satisfactory

18 TOOI^MAKING

results if given the same consideration a careful workman is supposed
to give any tool or machine used for accurate gaging. Fig. 13 shows
a pyrometer that may be employed in gaging the temperatures of
four different furnaces. Each furnace is numbered and its fire end
ia joined by means of wires to the proper connections on the
pyrometer. By turning the pointer to the proper number, the
temperature of that furnace is shonn on the dial of the gage.

Fig. 14 illustrates another stjle of pyrometer which gages tem-
peratures to 3000° F. By use of the switchboard shown in Fig. 15,

this gage may be used to determine tne temperatures of eight
fum&ces.

Fig. 16 shows an alarm pyrometer. This can be set to have
the alarm ring when the furnace temperature rises or falls beyond .
the desired limits. Such an instrument is especially desirable
where temperatures must not exceed certain limits, as is the case
with certain high-grade carbon and aihy steels, and where tools .
uul other articles that are to resist great strains are being hardened.

HardcnlnE and Tcmperint Crucible Tool SlccI
After the determination of the proper proportion of carbon, the
next important process is the hardening of the steel. This is sub-
divided into two main processes — heating, and subsequent cooling.

TOOL-MAKING 19

Heatinc* A piece of steel should never be heated more than is
necessary to. give the desired result. The heat required varies with
the make of steel, the amount of carbon it contains, the size and
shape of the piece, and the purpose for which it is to be used. Much
depends on giving a piece of steel a uniform heat throughout. The
edges and corners should be no hotter than the center, and the
interior should be of the same temperature as the surface; if not,
the piece is likely to crack in the cooling bath, on account of the
uneven changes which take place in the molecular structure. While
it is highly important that the steel be heated no more than is neces-
sary, yet it is of much importance that it be heated uniformly.

If the steel is placed in an ordinary forge, be sure that the air
from the blast does not strike it. For a large piece, build a big,
high fire; have it well heated through before putting in the steel.
Use the blast only enough to keep a lively fire, and see that the steel
is well buried in the fire in order that the air may not strike it.

Steel should always be hardened at a heat that leaves the grain
fine when the piece is broken. This condition can be determined
by hardening and breaking a small piece from the same bar.
A coarse grain denotes a heat higher than the steel should receive.

It will be found necessary, when heating some kinds of steel, to
put the articles in an iron tube so that the air cannot come in con-
tact with them; this is especially true when hardening such tools as
taps or formed mills, whose outer surfaces cannot be ground, because
the oxygen in the air, acting on the carbon at the surface of the piece
of steel, bums it out, leaving the surface decarbonized. Better
results can be obtained with any tool if it is kept from the action of
the fire when heating for hardening.

Cooling. When the piece is uniformly heated, it should be
plunged into a suitable bath to give it the proper hardness. It
must be worked rapidly up and down or around in the bath, to pre-
vent the steam generated by the red-hot steel from forming at
any point and so preventing the liquid from coming in contact with
the piece, and also to bring the piece constantly in contact with the
cooler parts of the bath. If the piece is long and slender, it must be
worked up and down; if it is short, with teeth on the outer edge, as
a milling-machine cutter, it should be worked around rapidly, so
that all the teeth may be cooled uniformly. If it b flat and has a

TOOL-MAKING

F'ui- 17. Tool with Outside Shoulder

hole through it whose inner walls must be hard, it should be swung
back and forth so that the bath may pass through the aperture and
at the same time strike both faces.

Delicate articles and tools having long projections or teeth,

should not be dipped into a bath
of very cold water or brine; for
such work, a tepid bath gives
better results.

If the tool is not to be har-
dened all over, and it is necessary
to heat a larger portion of it than
is to be hardened, dip the piece into the bath so that a trifle more
of the tool is immersed than is to be hardened, and then work it
up and down a little. If this is not done, there will be a line where
the piece is expanded on one side and contracted on the other. The

steel is likely to crack on

W/////M.

this line which is called a
water line.

When hardening a piece
having a shoulder A on the
outside, as shown in Fig. 17,
or inside, as shown in Fig. 18,
hardening should not stop at the shoulder, as the unequal strains
occasioned by the contraction of the hardened part at the shoulder
are likely to cause it to crack at that point. The piece ought not
to be hardened as high as the shoulder; but should it be necessar/

Q-* mjjwjjM/J i /iJi/iA ^o do so, it is well to

harden a little beyond.
A very satisfactory
method, when sharp
corners with sudden
changes of sizes occur, as
shown in Figs. 17 and 18,
consists in placing a ring
of wire in the shoulder, as shown at a or &, Fig. 19. Usually, the
piece will be made as at c, for the sake of strength, but when two
shoulders come in line as shown at a and 6, wires may be placed at
both shoulders. The wires, heating with the work, will be red hot

Fie. 18. Tool with Inside'ShouIdcr

'^^^^^^^w^mm mE^''v/////////M

Fig. 19. Use of Wire Ring in Hardening Piece with

Shoulder

TOOL-MAKING Jl

when the piece is dipped into the bath, and will prevent the w»ter
attacking the steel too suddenly in the shoulders.

Citric Acid Bath. An excellent bath for hardening small pieces
may be made by dissolving one pound of citric acid crystals in one
gallon of water. The liquid should be kept tightly covered when
not in use, or it will evaporate. Small tools heated to a low red
heat and dipped into thb solution harden more uniformly than
when immersed in clear water.

Pack Hardening. This method givres excellent results with
pieces that cannot be hardened by the methods ordinarily employed
without risk of springing or cracking. The article is packed in an
iron box, with some carbonaceous material, and subjected to the
action of heat, to allow it to absorb enough carbon to harden in oil.
While this method is not generally used, it is very valuable when
hardening such pieces as milling-machine cutters, blanking dies for
punching presses, gages, and taps, where it is necessary that the
diameter and pitch should not be altered. The carbonaceous
material is charred leather, which should be ground or pounded verj^
fine (usually about one-half the size of a pea). An iron box some-
what larger each ^ay than the piece to be hardened, should be
selected. A layer of the packing material one inch deep should be
placed in the bottom of the box, and the piece of steel laid on this;
the box should then be filled with the packing material and tamped
down. The space between the cover and the box should be filled
with fire clay, which seals it so that the gases in the box cannot
escape and the direct heat of the fire cannot get into the box.

It is much more economical to pack a number of pieces at a
time, as several may be hardened at the cost of one, and at a saving
in packing material. The pieces should be wired with ordinary iron
binding wire of a size sufficient to sustain the weight when the wire
is red hot, one end of the wire projecting over the outside edge of
the box and covered with the luting of fire clay. Several holes should
be drilled near the center of the cover for test wires, as in annealing.
The wires should extend to the bottom of the box which may now be
heated sufficiently to charge the pieces with carbon. As steel does
not commence to absorb carbon until it is red hot, the time is deter-
mined by means of the test wires as described under "Annealing".
For ordinary tools J ihch io diameter and under, run from 1 hour to

22 TOOL-MAKING

1| hours after they are red hot; pieces from \ incli to 1 inch in diam-
eter, 2 to 2) hours; pieces from 2 to 3 inches in diameter, 2} to 4
hours. This schedule must be varied according to the nature of
the work.

After remaining in the furnace the desired length of time, the
box should be taken out, the cover removed, and the piece taken
out by means of the wire attached to it. It should then be immersed
in a bath of raw linseed oil or cottonseed oil, and worked around
until the red has disappeared. Finally it is lowered to the bottom
of the bath and allowed to remain until cold.

When a piece of steel 1 inch in diameter, or larger, is hardened,
it should be reheated over the fire immediately on being taken out
of the bath; this is to avoid cracking from the strains caused by
molecular changes which take place after the outside surface is hard-
ened and unable to yield to the internal strains. Reheating the
surface to a temperature of about 212 degrees will accomplish the
desired result without materially softening the steel.

Although charred leather is the carbonaceous material usually
employed in pack hardening, it is not advocated for steel con-
taining more than 1} per cent carbon. If steel contains a larger
percentage than this, the packing material should be charre<l
hoofs, or charred hooh and horns. The charred leather may
be used over and ovei , by adding fresh materital as the old wastes
away. It is advisable to place the fresh material in contact with
the steel.

Tempering. The hardening of a cutting tool makes it too brittle
to stand up well when in use, and consequently it is necessary to
reduce the brittleness somewhat. This process of softening, known
as drawing the iempert is accomplished by reheating to the proper
temperature, ordinarily detennined by the color of the surface of
the tool which must be brightened previous to the operation. As
the piece of steel is heated, a light, delicate 6traw color appears;
then, in order, a deep straw, light brown, darker brown, light purple,
dark purple, dark blue, pale blue, blue tinged with green, and, finally,
black. When black appears, the temper is gone. These colors fur-
nish a guide to the condition of hardened steel, and indicate the
tempers attained with the degrees of temperature used in the
various connections shown in Table I.

TOOL-MAKING

TABLE I
Color Indications of Temper

Color

Heat
(Degrees
Ffthren-

heit)

Usage

Straw, light

Straw, deep

Brown

Purple, light

Purple, dark

Blue, dark

Blue, pale

Blue, tinged with green

430
460
500
530
550
570
610
630

Lathe and planer tools ; scrapers for brass ; etc.
Milling cutters; reamers: large taps; etc.
Twist drills; drifts; flat drills for brass; etc.*
Augers; screw slotting saws; etc.
Saws for wood; cold chisels; screwdrivers; etc.

Heating in OH, When steel is tempered in large quantities the
method just described is expensive. It is not, moreover, so reliable
as heating the articles in a kettle of oil, using a thermometer to indi-
cate the temperature. A piece of perforated sheet metal or wire
cloth should be used to keep the articles two or three inches from the
bottom of the kettle. A perforated sheet-iron pail two inches
smaller in diameter than the kettle, resting on a piece of iron, or a
frame placed in the bottom, will keep the pieces from the sides and
bottom of the kettle. The thermometer should be placed in the
kettle outside the pail, in order that the bulb may be at the same
depth as the lower pieces.

Spring' Tempering, A piece of steel may be spring-tempered
by first hardening and then drawing the temper to such a degree that
the piece, when bent, will return to its normal shape after the pres-
sure is removed. This may be accomplished by covering the surface
with tallow or some animal oil, and then heating until the oil catches
fire from the heat in the piece.

Casehardening. Heating with Poivdered Cyanide of Potaif'
sium. When an article of wrought iron or machine steel is to have
a hard surface, it is treated while red hot with some material that
forms a coating or case of steel, which hardens if dipped into water
while red hot. Small articles, such as nutS) screws, etc., may be
casehardened by being heated red hot and covered with a thin layer
of powdered cyanide of potassium. When the cyanide of potassium
melts, the article should be heated.red hot again and plungied into
water. Care should be exercised when using the cyanide, as it is
extremely poisonous.

24 TOOL-MAKING

It is sometimes desirable to harden a piece by this method,
and to have the surface colored. This may be accomplished by
having the surfaces first perfectly clean and well polished. Then,
when heated, and cyanide has been applied and allowed to "soak m*\
the piece is dipped into a bath of clean water. Before dipping, place
a piece of pipe in the water, blow through the pipe, and dip the
article down through the water where the air bubbles are coming to
the surface. The air in the water helps to produce a mottled appear-
ance on the surface.

Heating with Bone and Charcoal. The process described is
suited for hardening a few pieces quickly, but it is not recommended
for large quantities of work. When many pieces are to be case-
hardened at a time, the following method will be found less expen-
sive and far more satisfactory:

Granulated raw bone and granulated charcoal are mixed in
equal quantities, or one of the several good commercial case-
hardening compounds now on the market may be used. Some of
these compounds are more rapid in action than bone, and most of
them are cheaper. But whether one of these or bone is used, the
same general instructions are to be observed.

A layer of the mixture is placed in an iron hardening box to the
depth of 1 or 1 1 inches, and on this the articles to be hardened are
placed. The pieces should not come within i inch of each other, or
within 1 inch of the walls of the box at any point; they should be
covered with a layer of the mixture to the depth of J inch. Suc-
cessive layers of articles and mixture are placed in the box up to
within 1 inch of the top, the remaining space being filled with pack-
ing material; the cover is then put in place and the edges luted with
fire clay. Test wires should be used as described for annealing.
The heating must be timed from the moment when the contents of
the box are red hot, as determined by the test wires. The length
of time the work is allowed to run while red hot depends upon the
desired depth of the hardened surface; generally carbon will pene-
trate wrought iron J inch in 24 hours; but as it is rarely necessary to
harden deeper than A inch, the work may be kept red hot from
three to four hours. With small pieces, the contents of the harden-
ing box may be dumped into a tank of nmning water; if the pieces
are large, it is necessary to dip them one at a time just as in the case

TOOL-MAKING

of tool steel. For extreme toughness, the pieces, if small , may be dumped
into a perforated sheet-metal pan and the packing material sifted out,
after which they should be placed in a bath of oil. If not sifted out,
the packing material will stay at the top of the oil and set fire to it.

When a fine grain and strength are desired in the casehardened
portion, it is advisable to pack the articles in the hardening box as
described, then to heat them in a fire for a period that insures the
desired depth of penetration of carbon. The work is then allowed
to cool in the box, after which it is removed, heated in the fire, and
hardened by dipping in the
water or oil bath. ^ "

At times, charred bone
should be used instead of raw
bone, as the charred bone makes
the hardened article stronger.
For colored surfaces charred bone
mixed with charred leather is
extensively used. If we wish to
Iiarden for colors, it is neces-
»sary to employ comparatively

low heats and to hold the box , V///y////////^^r^

W5Q

/■

WAURPtPe

^AiR Pipe

Fig- 20. Hardemng Batb with Air Supply

very clpse to the top of the bath
when the work is dumped, in ■
order that the pieces may not
be exposed to the oxidizing
action of the air. It is not
advisable in making colored sur-
faces to allow air to come in contact with heated work passing from
the box to the bath, but if air is introduced into the hardening
bath excellent results may be obtained.' In Fig. 20 is shown an
air pipe which enters the bath with the w^ater supply, the air being
forced in by a pump.

In order that work may not go into the bath in a mass, the con-
tents of the box should be shaken out, a few pieces at a time, or
wires should be located along the top of the tank to separate the
articles so that the liquid can act on each piece. The bath must be
deep enough to allow the articles to chill below a red before striking
the bottom, or unsatisfactory results will follow.

26 TOOL-MAKING

Heataif in Mttitd Cyanic of Pobumm, Cyanide ot potas-
uum tnay be melted and heattd red hot in a cest>iroa crucible or pot,
and piecea ot work suspended in it until they are red hot, when they
should be removed and plunged Into the water to harden.

Beautiful colors may be obtained by this method, if the surfaces

o( the work are nicdy polished and cleaned before it la placed in the

cyanide. The beat should be low, and the articles should be passed

through a spray and then into a tank ot clear water. In order to

get the spray, Fig. 21, it is necessary to have a. supply pipe coming

|. down from above the tank with

I the end so flattened as to make

t\ a long and very narrow opening.

If colors are wanted, and a

hardened surface b not, use in

the cnunble what b known as

"50 per cent" fused cyanide.

Unless the steel is sufficiently

high in carbon to harden of

itself; the surfaces will not

Altoy Steel I
The tool steel that is genei^
ally used for cutting tools is
made by the crucible process.
If the steel depends on the car-
bon in it for ita hardening qual-
ities, it is called carbon tool lAeel.
Hi^-carbon steels harden better, stand higher speeds, and allow
heavier cuts than the same quality of steel with lower carbon
percentages.

In order to produce a steel that will stand higher speeds and
heavier cuts than carbon steel, various elements have been added.
Each of these steels are generally given a distinguishing name, usually
that of the added element, such as vanadium steel, manganese
steel, silicon steel, tungsten steel, etc.

Vanadium steel b especially adapted to such toots as taps,
reamers, broaches, and some forms of dies.

//////lll',l',U\\\

TOOL-MAKING 27

Tungsten Steel. If tungsten is added in a small percentage, a
steel is produced that allows higher speeds and will cut harder stock.
Steel with a- higher percentage of tungsten hardens if heated red
hot and allowed to cool in the air, but better results follow if it is
cooled in an air blast, or in oil. This is called air'hardemng or self-
hardening steel. Tools made from air-hardening steel allow speeds
from 50 to 60 per cent higher than can be obtained from similar tools
made from carbon steel. This steel proves particularly satisfactory
for heavy roughing cuts, but not for finish cuts as it does not hold
a fine cutting edge. It has given way to the modem high-speed
steel in most shops, but for certain classes of work it is still used to
some extent.

Oil-Hardening Steels. Carbon tool steels, when hardened by
the ordinary fire-and-water method, show a tendency to get out of
shape, or to change in length measurements. To do away with
this difficulty, oil-hardening steels are extensively used in many
shops for making taps, dies for screw cutting, blanking dies for
punch-press work, etc. Under many conditions these steels work
very satisfactorily, if a brand adapted to the particular work to be
done is procured. The method of treatment for the steel of differ-
ent makes varies so much it would not be wise to attempt to give
any specific instructions without knowing the particular make of
steel and the purpose for which it b to be used. The makers of these
special steels always furnish instructions for working their particu-
lar brands, so there need be no difficulty encountered in their use.
Directions should be carefully followed, except in cases where experi-
ence has shown the advisability of a different method. To secure
the best results, a furnace equipped with a good pyrometer should
be used, as this enables the operator to adjust the temperature to
the proper point.

To show the variation in treatment for the different makes of
alloy steels, we shall cite two cases, both well-known brands.
One make that is specially adapted for taps, dies, and similar
tools should be hardened at a temperature of 1350** F., while
another make, to be used for the same purpose, shows best
results when hardened at 1500'' F., a variation of 150 degrees.
Yet both steels give excellent results when treated according to
instructions.

28 TOOL-MAKING

Modem High-Speed Steels

If, besides tungsten, certain proportions of chromium are added,
a steel b produced that has revolutionized machine-shop methods.
It allows extremely high speeds, heavy cuts, and coarse feeds. It is
possible with a good grade of high-speed steel to increase the cutting
speed of tools from 50 to 200 per cent above that possible with
ordinary carbon steel. Unlike carbon steels, the high-speed steels
grow harder as they become heated, until they are red hot when
they are soft enough to forge.

Forging. This steel should not be heated too rapidly; in fact,
it requires comparatively slow, careful heating in a good, heavy fire
of blacksmithing coke. It should be worked at a high heat, with
rapid blows, which should cease as the temperature goes down.
Never hammer when the steel is at a low red. Although the steel
should be reheated as soon as it is below a forging heat, as much as
possible should be done, at each heat.

After forging, the tool should be reheated to a high red heat,
and allowed to cool slowly in the air; this is done to remove forging
strains which might cause the steel to crack when hardened. When
the tool has cooled down below a red, place it in the fire, and reheat
for hardening.

Variations in Hardening for Different Tools. When hardening
tools made from high-speed steel, it is necessary to vary the treat-
ment to suit the particular class of tool. For instance, it is cus-
tomary to heat ordinary lathe and planer tools nearly to the fusing
point; in fact they are usually brought to a temperature that causes
the edges and corners to drip, then placed in a strong blast of air,
or dipped in cottonseed oil. When hardening reamers, taps, drills,
miUing^machine cutters, and other tools having slender projecting
portions, or standard forms, it is not possible to heat them to such a
temperature and preserve the shapes and slender portions, as they
would be melted away; neither can they be cooled in an air blast,
as the action of the air is to oxidize the slender portions and so to
render the tool unfit for use. Most tools used in the lathe, planer,
and similar machines, can be ground to shape after hardening, and
the melting-away of the edges and comers does little or no harm;
but taps, dies, reamers, and formed milling cutters must retain their
shapes as they cannot be ground to form after hardening.

TOOL-MAKING 29

Lathe and planer tools of ordinary design may be heated in a
fire of coke or well-coked blacksmith's coal, in. an ordinary Forge,
although better results are obtained if they are heated in a Furnace
specially designed For high-speed steel; long slender articles, such as
taps and reamers, give best results if heated in a furnace oF the design
shown in Fig. 22. This furnace is so constructed that the ftame
moves around the walls thus leaving a space at the center free
from the direct flame. The tools are suspended From the top as
shown and in the center, thus preventing oxidation of the steel.

iliUing-machine cutters, punch-press dies, and many other forms
of tools should be heated in an oven furnace as shown In Fig. 23.
Tools heated in this Form oF Furnace should not be placed on the bot-
tom but on a piece of fire brick, as shown.

As the temperature in a furnace being used for heating high-
speed steel is extremely high, cold tools should not be placed directly
in the furnace, but should be preheated in an open fire or in a slow
fire of some kind, brought to a red heat, and then put into the special
furnace. The sudden and unequal expansion of a piece of cold steel
when placed in contact v'^h a very high temperature, would cause
it to cragk in various paKs.

30 TOOL-MAKING

Tempering for Delicate Tools. When taps, milling-machine
cutters, snd other tools having weak projecting portions are made
from this steel, it is necessary to draw the temper in order to reduce
the Brittleness to « point where the tools will stand. To accom-
plish this, the surface is brightened and the temper drawn in the
tisual manner. The shanks of taps are plunged into red-hot lead,
and allowed to remain there until they are red, when they are
removed and buried in dry
lime. The bodies of the taps
are allowed to remain in the air.
Annealing- High-speed
steel is annealed by being
packed in an iron box with
dry fire clay or a mixture of
lime and powdered charcoal,
or some material that will
exclude the air. A cover is
placed on the box and luted
with fire clay, which is allowed
to dry before the box is put
into the furnace. It is neces-
sary to heat this steel more
than ordinary steel, and to
maintain the high heat longer.
Generally it is heated to a
yellow heat and allowed to
remain at this temperature for
a length of time that varies
FiB. 23. Ovci. ^mjM^far HMdcDini Miiiine ^^y, ^he size of the pieces.
cou/[«> cif ^™r,M»^^Fj.rn«c c»p-p=»v. For small pieces, 2 or 3 hours

will suffice, but for extremely
large blocks the high temperature must be kept up for 12 or 15
hours — after they are heated through. The steel should be allowed
to cool slowly.

Pack Hardening. In many sliops difficulty is experienced in
hardening such articles as milling-machine cutters, forming tools for
screw machines, and similar tools made from high-speed steel. The
work can be done with uniformly satisfactory results if the tools are

TOOL-MAKING 31

placed in an iron hardening box and surrounded with charred leather,
a cover placed on the box and sealed, the whole being then put into
the furnace and heated to a yellow heat. The articles should be
kept in the furnace at this heat for several hours, the time depending
on their sizes and shapes. For forming tools and milling-machine
cutters of ordinary size 2 or 3 hours answer very well; smaller pieces
should not be left in so long.

When the tools have been at the yellow heat for the proper
length of time, they should be removed and plunged into a bath of
raw linseed oil, and worked around in the oil until cool.

Merits of High-Speed Steel Tools. The result* obtained from
the use of high-speed steel tools are dependent in a very large meas-
ure on the way in which the tools are made and used. As they are
principally valuable for roughing purposes, it is apparent that they
should be made strong and of such shape as to bring as, little .strain
as possible on the machine. When forging, the life of the tool
should be considered, and a shape adopted that will permit a number
of grindings. If the top of the cutting end of a tool is made of the
same height as the top of the tool shank, it can be ground but a few
times before it is necessary to dress it again, and the tool is conse-
quently short-lived. If, however, the top of the cutting end of the
tool is made higher than the top of the tool shank, it can be ground
a number of times, so that the life of the tool is increased and the
expense of forging proportionately lessened.

The use of high-speed steel for cutting tools has, as stated else-
where, revolutionized maohine-shop methods. IVIodern competition
renders it necessary in mft^iy plants to reduce the cost of labor to
the lowest possible limit, and the use of tools- that allow extremely
high speeds has done much toward making this reduction possible.

Shop System in Use of Steels. All steels are not equally good
for all classes of work. Some work better on cast iron, while others
are better adapted for steel cutting. In order to get the highest
efficiency possible it is advisable, where several different metals are
machined in quantities, to employ tools that are specially suited to
the different kinds of work, each tool having the name of the steel
from .^hich it is made plainly stamped on it. However, when most
of the material machined is cast iron, special tools for steel cutting
need not be made as the tools used for cast iron will answer.

TOOL-MAKING

If several kinds of steel are used in a shop, each tool should
be given a distinguishrtig mark, as one tool might be made from
ordinary crucible steel, another from a steel containing a small
amount of tungsten, and still another from high-speed steel. Tools
made from each of these grades require difTerent treatment and
unless they are marked or a record of them kept, it is impossible
after a time to distinguish between them.

Tungsten steels may be recognized, when grinding on an abra-
sive wheel, by the appearance of the spark, which will l)e blood-red
in color and round in form; carbon steel, wIkmi ground, gives off a
yellow spark which bursts in the air.

STANDARD TOOLS

DRILLS

The forms of drills commonly used in the machine shop are the
flat drill, straightway drill, single-lip drill, and twist drill.

Flat Drills. Flat drills, intended for use in the engine lathe for
chucking, are usually forged to shape in the forge shop. After center-

Tjrj]

'■ i,,"'i,

>»

Fig. 24. Flat Drill for Chuckinc ia Lathe

vug the end, which rests on the tail center of the lathe, the lips are
ground to shape, and the drill is ready for use. A drill of this
description is shown in Fig. 24.

If it is necessary to have the drill cut almost exactly to size, it
should be forged somewhat wider than finish size, and the edges
turned in the lathe, as in Fig. 25. The projection A must be left on
the cutting end to provide a center for turning. If the drill is to be
ground to size alter hardening, the projection must be left on until

TOOL-MAKING 33

the grinding has been done, but ordinarily this class of drill is not
intended to cut exactly enough to require grinding to size.

filing. If the edges of the drill are not to be ground to size,
they should be drawfiled a small amount to avoid binding. The
filing should not come within i^ inch of the edge, and should be only
a small amount — .003 or .004 inch will be found sufficient; if given
too much relief, the drill will jump and chatter. The shank should
be somewhat smaller than the cutting end — A to ^^j inch — in order
not to touch the walls of a hole drilled deep enough for the shank to

6J"
64

. 3

Fts. 23. Maklns Flat Drill for Chucking

enter. The center in the shank end should be large, to insure a
good bearing on the tail center of the lathe, as shown at A, Fig. 24.
Hardening. In hardening, the drill should be heated a low red
to a point above the cutting end, preferably about one-half the length
of the portion turned smaller than the ends. When dipped into the
bath, it should be plunged about one inch above the cutting end.
To insure good results, it should be worked up and down and around
in the bath, which may be either water or brine. /The temper
should be drawn to a brown color.

Fig. 26. Usual Form of Tranafer Drill

When a fiat drill is intended for use in a drill press, the shank
is left round, in order that it may be held in a'chuck orv collet.

Transfer Drill. Another form of flat drill, termed a transfer
drill, is very useful when a small hole is to be transferred from a
larger. The shank C, Fig. 26, may be made of any convenient size;
the portion B is of the size of the larger hole, while A is of the size of
the hole to be transferred, and is a short flat drill.

If a lathe is used having draw-in split chucks, the drill may be
made from drill rod which should be enough larger than finbh size

TOOL-MAKING

to allow B to be turned to insure its running true with A; the cutting
part A may be milled or filed to thickness. The cutting lips are
then backed off, and the drill hardened high enough up so that A

Fi«. 27. Straightway or Straight Fluted Drill
Courtety of Union Twist Drill Company, Athol, Ma»»acktuiU$

and B are hard, as the portion A does the cutting, while B, being a
running fit in a hole, is likely to rough if it is soft.

To harden, the drill should be heated in a tube and dipped in
water or brine, and worked up and down, to avoid soft spots caused
by steam keeping the water from the metal, which sometimes happens

when a piece has different sizes

ceo

rig. 28.

Stock, Drilled with Straightway
Drill

close together. The cutting por-
tion A should be drawn to a deep
straw color; B should be left as
hard as possible, to resist wear.
Straightway or Straight Fluted
Drills, These drills have the
flutes cut parallel to a plane passing through the axis of the drill, as
shown in Fig. 27. They are used in drilling brass, iron, and steel,
when the holes break into one another, as shown in Fig. 28.

The smaller sizes may be made of drill rod. After cutting to
length, the blank may be put in a chuck in the lathe and the end

pointed to the proper cutting angle.

When milling the flute, the shank

may be held in the chuck on the end

of the spiral-head spindle. The

head should be set at an angle that

makes the flute deeper at the cut-

ing end of the drill than at the

shank end; this causes an increase

of thickness at the shank and makes

the drill stronger than if the flute

were of uniform depth throughout. The milling cutter should be

of a shape that wilt make the cutting face of the drill a straight

line when the drill is ground to the proper cutting angle. The

Fig. 29. Cutter for Straightway Drill

TOOL-MAKING

comer should be somewhat rounded. The general shape of the
cutter is shown in Fig. 29.

Single-Lip Drill. For certain classes of work the single-lip drill
is very useful. Having but one cutting edge, its action is similar to

Fig. 31. Method of Making Smgle-Lip Drill

Fig. 30. Single-Lip Drill Used with Bushings

that of a boring tool used for inside turning in the engine lathe. The
body of the drill being the size of the hole drilled insures the cutting
of a straight hole, even in drilling work partly cut away, or castings
having blowholes or similar imperfections. This drill does not cut
as rapidly as the other
forms, and consequently t

is not used where a twist
drill would do satisfac-
tory work.

Fig. 30 shows a form
of single-lip drill to be used with a bushing. The steel should be
somewhat larger than finish size, in order that the decarbonized si:r-
face may be removed ; the cutting end A and the shank B should
be turned from .014 to .020 inch
larger than the finish diameter to M
allow for grinding after the drill Mm
's hardened. The portion C should
be turned to finish size and stamped.
In order that the drill may be
ground to size after it is hardened,
it will be necessary to face the end
back, leaving the projection con-
taining the center as shown at A,
Fig. 31. The cutting end should be
milled to exactly one-half the diam-
eter of B. After millmg, the face C should be drawfiled until it is
flat and smooth.

Hardening. When hardening, the drill should be slowly heated
to a low red^ a trifle higher than the portion that is to be cutting size;

Fig 32.

Method of Grinding Single-
Lip Drill

TOOL-MAKING

it should then be plunged into a bath of warm water or worm brine
in order to avoid so far as possible any tendency to apringbg or
cracking in the projection A. The tendency to crack is due to its
peculiar shape and the difference in its size and that of the drill.
After hardening, it may be drawn to a straw color.

GrindiTig. It is advisable to grind the shank first, in order that
the machine may be adjusted to work straight. After grinding the

shank and cutting end to she, the projection A may be grqund off,
and the cutting end given the required sliape, as shown in Fig. 32.

Giving Fake to Cvtting Face. When a single-lip drill b to be used
on iron and steel, and not upon brass. It may be made to cut more
freely by giving the cutting face a rake, as shown in Fig. 33, This
is done by milling the portion A to the proper dimension, which is
one-half the diameter of the blank. The end and sides of the drill
are now coated with the blue vitriol solution and the desired shape

marked out, after nhich the tool is plnctxl in the millingHnnchine
vise at the proper angle, and tl>e Ttqiiin-d amount of rnkc oblaincil
by means of small cnd-cutlcrs. After giving 'he ntciasiiry end
clearance, as shown in the two views of Fig. 33, the drill is ready for
hardening.

ItmeHed C^Ur. In order to adjust a drill of this kind to com-
pensate for wear, it may be mmle as shown In Fif. 34, in «lncli out-
quarter of the circumference plus the thickness of llie cutler to be

TOOL-MAKING 37

used, is cut away at A and a blade or cutter fastened in position,
the top face of which should be radial. To compensate for wear,
pieces of paper or thin sheet metal may be inserted under the blade.
When cutting away the portion A, three holes may be drilled, as
shown in Fig. 35.

If square comers are desbed, care should be taken that the
holes are located so that they will machine out when milling to the
proper dimensions. After drilling, the body of the drill should be
placed in a vise in the shaper, and by the use of the cutting-off tool
(parting tool) the portion removed; but as it would be impossible
to cut to finbh dimensions, it will be necessary to finish with snAill
end milling cutters, holding the tool in the chuck on the spindle of
the spiral head. After machining one surface, the spindle may be
revolved one-quarter turn and the other surface machined; this

Ti$. 36. DUgnun Showing Method of Cutting Out Quadrant
for loaerted Cutter

insures square comers, and two surfaces at right angles to each
other. The surface on which the cutter is to rest should be cut
below the line of the center, so that the top edge of the cutter may be
radial — that is, it should be cut the thickness of the cutter below a
line passing through the center. Fig. 34.

The cutter should be made of tool steel and two holes drilled
for the fastening screws. When the cutter has been fastened in
position, it may be turned to the proper diameter by mnning the
body of the tool in the steady rest of the lathe. Care should be
used not to cut into the body or holder. After turning to size and
facing the end square, the cutter may be removed from the holder,
and necessary clearance given the end by filing; the outer edge may
be drawfiled in order to smooth it, and a slight clearance given to
prevent binding. This is done by removing a trifle more stock at
the bottom than at the top edge. To harden, it should be heated
to a low red heat and dipped in lukewarm water; the temper should
be drawn to a straw color.

38 TOOL-MAKING

Twist Drills. It is, in general, cheaper and more satisfactory to
buy twist drills than to attempt their manufacture in the ordinary
machine shop; but at times some emergency may call for a special
size or length of drill which it will be necessary to make.

For the smaller sizes, it is best to use commercial drill rod.. For
drills larger than }-inch diameter, select larger stock and turn it to

F«. 36. Blank for Twist Drill

the desired size. In the case of the latter drills, if true holes of the
size of the drill are required, it is advisable to turn them .010 to .015
inch larger than finish size, and grind to size after hardening. A
projection. Fig. 3,6, containing the center,' should be left on the cut-
ting end of the drill until the grinding has been done. After cutting
the flutes and grinding the drill, the projection may be ground of!
and the cutting lips ground to the proper shape, as shown in Fig. 37.
When making drills of the smaller sizes from drill rod, the blanks
may be cut and pointed to the proper angle on the cutting end; this
may be done in the lathe, the blank being held in a chuck. The
proper angle is 59 degrees from one side of the blank. When milling
the flutes of a twist drill on a universal milling machine, the shank
of the drill, if straight, may be held in a chuck or collet of the rjght
size, and, if very long, may be allowed to pass through the spiral head.

Fig. 37. Finished Twist Drill
CourUay of Union Twial Drill Company, Athol, iiM»aehuteU»

Milling Flutes. The accompanying explanation and table are
taken from the Brown and Sharpe Manufacturing Company's book,
"Construction and Use of Milling Machines", and are intended to
use with the cutters manufactured by them for making the flutes in
twist drills.

The cutter is placed on the arbor directly over the center of the drill, and
the bed is set at the angle of the spiral, as given in Table II.

TOOL-MAKING

TABLE II
Data for Cudini Twiit Drilli

D.««c.

T..t.-

ScciMii

o.«

Akoli

or"™

Ge.. D»

■^JiTf'

Wo.-

ECDD

Stdd

Sc...

Smil^l

. ,

100

16= 20'

1 12

100

I9=2ff

19° 25'

21'

2 VI

20"

.23

3 24

21'

20" 10'

i 17

20° 30-

488

20"

20' 12'

,,o 3(,,

(

19=20'

.62

7 f,2

19; so;

™

8 33

19= 20'

ength at the place wbere t>

TOOL-MAKING

tbe ipirtl liMd is elevated eomewhAt, depending on the length of the flute to be
cut; when len than 21mchee in length, the angle ahould be | degree; 5 inches and
over in lenglh, 1 degree. Usually this will be found satisfactory, but for extremely
long drills the elevation must exceed these amounts. The outer end of the drill
must be supported as shown in Fig. 38; and when small, should be pressed
down firmly until the cutter has passed over the end.

It is somewhat better to use left-handed cutters, so that the cut may begin
at the shank end, in order to lessen the tendency to lift the drill blank from the
rest. When laige driUs are held by the centers, the head diould be depressed in
order to decrease the depth of the groove as it approaches the shank.

Backing Off Rear o/ Lip, Another very important operation
on the twist drill b that of backing off the rear of the Up, to give it
the necessary clearance. In Fig. 39 the bed b turned to about }
degree, as for cutting a right-hand spiral; but as the angle depends

Fig. 39. *'BMkiBg or* a TwiM DriU

on several conditions, it wUl be necessary to determine what the
effect will be under different circumstances. A study of the figure
will be sufficient for thb by assuming the effect of different angles,
milb, and the pitches of spirals. The object of placing the bed at
an angle b to cause the mill F to cut into the lip at C and just touch
the surface at E\ The line R being parallel to the face of the mill,
the angular deviation of the bed in comparison with the side of the
drill b clearly shown at A,

While the drill has a positive traversing and relative movement,
the edge of the mill at C must always touch the lip a given distance
from the front edge, thb being the vanbhing point; the other surface,
forming the real diameter of the drill, b beyond the reach of the
cutter, and b left to guide and steady it while in use. The point E,

TOOL-MAKING 41

as shown in the enlarged view, Fig. 39, shows where the cutting
commences, and its increase until it reaches a maximum depth at
C, where it may be increased op diminished according to the angle
employed in the operation, the line of cutter action being repre-
sented by 11.

Before backing off, the surface of the smaller drills in particular
should be oxidized by heating until it assumes some dbtinct color to
show clearly the action of the mill on the lip. of the drill, for, when
satisfactory, a uniform streak of oxidized surface, from the front edge
of the lip back, is left untouched by the mill, as represented in
the cut at E,

If the drills are to be ground without being centered, pointed
projections with a 60-degree angle may be made on the ends, as
shown in Fig. 39; these projections may be run in female centers in
the grinding machine. In grinding, if the drills are tapered back
about .003 inch in 6 inches, it will be found that the clearance thus
obtained will cause them to run much better.

Hardening, Twist drills are hardened by special processes
which, generally speaking, are not understood outside the shop
where the drills are made. Very good results, however, may be
obtained if the drills are heated somewhat and dipped into a solu-
tion of the following:

Pulverized charred leather 1 pound

Fine family flour 1| pounds

Fine table ealt 2 pounds

The charred leather should be ground or pounded until fine enough
to pass through a No. 45 sieve. The three ingredients are thor-
oughly mixed while in the dry state, and water is then added, slowly,
to prevent lumps, until. the mixture formed has the consistency of
ordinary varnish.

After the drill has been dipped in the mixture it should be laid
in a warm place to dry; when thoroughly dried it should be heated
in a tube, or preferably in a crucible of red-hot lead, until it is a •low
red, and then plunged into a bath of lukewarm water or brine; small
drills may be dipped in a bath of oil. The drill must not be put in
red-hot lead until the coating is thoroughly dried, as the moisture
may cause minute particles of lead to fly in all directions, endanger-
ing the eyes of the operator. After huidening, the temper should

TOOL-MAKING

be drawn to a full straw color. If several drills are hardened at one
time, the temper may be drawn by placing them in a kettle of oil
over a fire, gaging the amount of heat by a thermometer, as explained
in the section on the tempering of tool steel.

A bath that insures excellent results when drills and similar
articles are hardened, is shown in Fig. 79. This bath has perforated
pipes extending up the sides, as shown. The water from the perfora-
tions is projected against the drill and to the bottoms of the flutes,

so that uniform results are assured.

Grinding, Although most shops are
provided with a special machine for grind-
ing twist drills, yet at times it is neces^
sary to grind such tools by hand, and
every workman should practice until he
is able to do this properly without the
use of a special machine. The cutting
edges must make a proper and uniform
angle with the longitudinal axis of the
drill ; they must be equal in length, and
the lips of the drill su£Bciently backed off
for clearance; otherwise they will not cut
easily, or if they do cut, they will make
a hole larger than the size of the drill.
Drills properly made have their cut-
ting edges straight when ground to a
proper angle, which is 59 degrees, Fig. 40.
Grinding to an angle less than 59 degrees
leaves the lip hooking, which is likely to
produce a crooked and irregular hole.
A very satisfactory form of an angle-gage for this work is shown
in Fig. 41. The graduations on the upper part of the gage show
when the lips are ground to an equal length, which is essential if the
drill is to cut the proper size. As the operator becomes experienced,
he can gage the angle and length of lips very accurately by the eye,
but until he has had the necessary experience, it is advisable to use
some form of gage.

Drills for Deep Holes. A good drill for use in drilling deep
holes, in such work as gun barrels, machine spindles, and similar

Fig. 40. Checking the Proper
Ang]e for Twist Drill

TOOL-MAKING

pieces, is shown in Fig. 42. This tool was brought out by the Pratt

and Whitney Company, of Hartford, Connecticut, and is used in

connection with their gun-barrel drilling machines. It b especialljr

valuable because it produces » straight,

true hole. It has but one cutting lip as

will be noticed by referring to the end view

of the tool. In milling the groove that

forms the cutting edge, the surface b, is

exactly on the center. An oil groove c is

provided, as shown, through which oil may

be forced to the cutting edge by means of

a powerful pump. The oil is under pressure

varying, according to the diameter of the

drill, from 150 to 200 pounds per square

inch. After lubricating the cutting edge it

carries the chips back through the chip

groove and deports them outside of the

drilled hole. For drilling very large holes

the cutting edge of the drill is usually made

with a series of step-like cuts, as shown in

Tig. 43, which break the chips so that they

can be carried back through the chip groove. *'* ^'foiTv^iM'^"**

In sharpenirigthe drill, the point is not
produced in the center, but at one side, as shown; this is one of
the reasons for the drill's cutting true, as the projection A in work
acts as a support. When using this style of drill it is customary to
run at high speed and emi>loy a fine feed.

Because of the position of the point it is necessary to run the
drill, when starting, through a bushing, or V-guide, as otherwise it

would not be possible to produt

a hole concentric with the circi

TOOL-MAKING

\ =

Use of High-Speed Steel. High-speed steel is used very exten-
sively in making drills, especially of the larger sizes. They can be

run at very much greater speed
^ than those made from carbon
steel, and used for drilling harder
materials. At times trouble is
experienced when using high-
speed drills for very deep vertical
holes; but the trouble may be
obviated by forcing a stream of
oil down into the hole with suffi-
cient force to cause the chips to
come to the surface of the work,
thus giving the oil free access to
the cutting lips.

When hardening drills made
from high-speed steel, first pre-heat in a slow fire to a low red, then
suspend in a furnace of the design shown in Fig. 22 and heat to a

unifofm temperature of
2100° F., finally immersing
in a bath of cottonseed oil.
If possible, use a bath hav-
Fi*. 45. Twbt Drill Formed from Flat Stock !"« perforated pipes up the

wmtmmmm ^mmammL

Fig. 44.

Section of Oil Bath with Per-
forated Side Pipes «

Fig. 46. Twist Drill with Angle of Spiral Changed for High-Speed Work

sides, as shown in Fig. 44, so that the oil may get to the bottom
of the flutes and harden all portions of the drill. In order that

TOOL-MAKING

the drill may not be brittle after the hardening operation, the temper
should be drawn to 460'' F.

Tools for Rapid Drilling, For rapid drilling there are various
styles of twbt drills. Fig. 45 shows one made from flat stock twisted
to form the flutes, which is especially satisfactory for certain classes
of work. Fig. 46 shows the regular design except that the angle or
spiral is 32 degrees instead of 25 degrees. The quick twist permits
more rapid cutting and greater production by the operator.

REAMERS

A reamer is a tool that makes a smooth, accurate hole. In
many cases, however, reamers are used to enlarge cored holes, or

Fif . 47. Solid Reuner

holes already drilled, without particular reference to the exact size
or condition of the hole. Reamers may be classified according to
shape as follows: straight reamers, taper reamers, and formed ream-
ers. Reamers are made solid, adjustable, and with inserted blades.
Solid reamers. Fig. 47, are so called because the cutting teeth
and head are made from one piece; they have no means of adjust-
ment as to size. The cutting teeth of the inserted-blade reamers
are made from separate pieces of steel and inserted in the head, as
shown in Fig. 48. The adjustable reamer may be made with inserted

Fit. 48. Reamer ^th Inserted Blades
Courtny of Brown and.Sharpe Mantk/itciuring Company, Providence, Rhode Island

teeth, or with cutting teeth solid with the head; but in either cas<^
it has some means of adjusting the size.

STRAIGHT REAMERS

Under this heading the following kinds of reamers are to be
found: ^uted hand reamers, fluted chucking reamers, rose reamers,
single-lip reamers, and three- and four-lipped roughing reamers.

TOOL-MAKING

Fluted Hand Reamers. This reamer is made straight on the
cutting lips, with tlie exception of a short distance at the end, A,
Fig. 49, which is slightly tapered in order that the reamer may enter

Fig. 49. Proper Proportions for Fluted Hwid R«ain«r

iKe hole. In making such reamers, use steel from A inch to \ inch
above finish size. Turn a chip off the outside surface to a depth of
A inch, and anneal; then turn A and /?, to sizes .010 to .015 inch
larger than finish size; turn. C to finish size; mill the end D square
for a wrench. The reamer is now ready to have the flutes cut.
Number of Cutting Edges. Fluted reamers designed to remove
but a small amount of stock, and intended to cut holes to an accurate
size, are rarely given less than six flutes. Below are given the
number of cutting edges advisable for solid reamers whose flutes are
milled by cutters made to give the proper shape:

Reamers |' to ^
Reamers i' to H
Reamers {' to 1"
Reamers 1^' to H"
Reamers l-ft" ^ 2^
Reamers 2^ to 3'

" in diameter should have 6 teeth
in diameter should have from 6 to 8 teeth
in diameter should have 8 teeth
in diameter should have 10 teeth
in diameter should have 12 teeth
in diameter should have 14 teeth

Formerly it was considered necessary to
have an odd number of cutting edges; but an
even number, if unevenly spaced, will be as
satisfactory. The chief objections to an odd
number are the difficulty experienced in
calipering, unless a ring gage is used, and the
great cost of grinding.

Fig. 50 shows a form of cutter that
makes a strong reamer tooth and allows the
chips to be removed very readily. These cut
the tooth ahead of the center, and should be
given a negative rake of about 5 degrees. In

general, a reamer will cut more smoothly if the tooth has a slight

negative rake, as it then takes a scraping cut.

Fig. 50. Shape of Cutter
for Re

lesmer

TOOL-MAKING

Depth of CvJt. With this form of flute, the depth of cut must be
so gaged that the land will be about \ the average distance from one
cutting edge to the other; if cut deeper, the teeth will be weak and
have a tendency to sprmg; if not so deep, there will not be room for
the removal of the chips. Below are tabulated the number of
cutters. Fig. 50, for various sizes of reamers.

No. 1 cutter outs reamers from \' to
No. 2 eutter cuts reamers from i' to
No. 3 cutter cuts reamers from i' to
No. 4 cutter cuts reamers from Y to
No. 5 cutter cuts reamers from f to 1'
No. 6 cutter cuts reamers from li^' to H'
No. 7 cutter cuts reamers from 1 A' to 21'
No. 8 cutter cuts reamers from 2\' to 3'

A' diameter

^'cLiftmeter

1^' diameter

H' diameter

diameter

Fig. 51. Reamer with Pint
Pair of Flutes Cut

Spacing of Teeth. In order that reamers may be calipered
readily when grinding, if the teeth have been unevenly spaced, the
teeth must be diametrically opposite each
other; the unevenness in spacmg must be
between adjoining teeth. This is done by
cutting one tooth, then turning the spiral
head of the milling machine half-way round,
by giving the index pin twenty revolutions,
and then cuttmg the opposite tooth. When
the flutes are cut in pairs, the number of
times the cutter must be set for depth of cut
b reduced one-half. Fig. 51 shows an end
view of a reamer having the first pair of flutes cut as described. The
irregularity of spacmg is obtamed by movmg the index pin a different
number of holes for each adjoining pair of flutes. This irregularity
need not be great, a variation of 2, 3, or 4 degrees from an angle cor-
responding to regular spacing, is generally regarded as good practice.

Finishing Processes. Hardening, In order that a reamer may
not spring when hardened, great care should be exercised in heating.
If a muffle furnace is at hand, a unLform heat can be obtained. If
heated in a blacksmith's forge, the reamer should be placed in a
tube to prevent the fire from coming in contact with the steel, and
should be turned frequently to secure unLform results. In cooling,
it should be held in a vertical position to avoid springing, and worked
up and down in the bath.

48 TOOL-MAKING

ir the reamer is one inch in di&meter or larger, it should be
removed from the hardening bath wheo it stops "singing", and
plunged into oil, and allowed to remain until cold. The temper may
be drawn to a light straw color. If reamers are hardened by the
pack-hardenbg process, the danger of springing is greatly reduced.

Siraightemng. The straightening should be done before drawing
the temper. When drawing the temper, the heat should be applied
evenly, or the piece will spring from uneven heating.

]f B reamer springs wliile hardening and tempering, it may be
straightened by the following method:

Plifce the reamer between the centers of the lathe; fasten a tool,
or a piece of iron orsteclhaving a square end, in the tool post, Fig-52,

placing the square end against the reamer at the point of greatest
curvature. The surface of the reamer should be covered with a thin
coating of sperm or lard oil. Willi a spirit lamp, a plumber's hand-
torch, or a bunsen burner, heat the reamer evenly until the oil com-
mences to smoke. Pressure may now be applied by means of the
cross-feed screw, slowly forcing the reamer over until it is bent a
trifle the other way. It should be cooled evenly while in this posi-
tion, after which the pressure may be relieved and the reamer tested
for truth. If it does not run true, the operation should be repeated
This method of straightening is equally effective when applied to
other classes of work.

Gnnding. Before grinding a reamer, be sure that the centers
of the grbding machine are in good shape; then clean the ccnterfi (rf

TOOL-MAKING

the reamers. The reamer should first be ground to run true. It
may be ground to within .001 or .002 inch of finish size, larger reamers
having the larger margin. In backing off a reamer tooth for clear-
ance, use an emery wheel of as large diameter as can be used without
striking the cutting edge of the next tooth. The correct clearance
is given by a finger which can be adjusted. Fig. 53 shows an end
view of a reamer being ground for clearance, together with the finger
and the emery wheel. The emery wheel should run in the direction
indicated by the arrow, in order that the pressure of the wheel will
tend to force the reamer tooth down on the finger B. To give clear-
ance, the finger is adjusted so that the cutting edge is below the line
of centers, as shown.
The lower the finger, the
greater the amount of
clearance. Unless a free-
cutting wheel, without
glaze is used, the temper
will be drawn, and the
reamer rendered worth-
less. To avoid soften-
ing the teeth, the stock
must be removed by a
succession of light cuts

going entirely around the reamer each time the adjustment is
changed.

A reamer will soon lose its size if the clearance is ground to the
edge of the teeth; consequently it is best to grind to within from
.01 to .015 inch of the edge, according to the size. The reamer is
then brought to an edge and to the desired size by oil-stoning. To
do satisfactory work, the stone should be free-cutting; a stone of
medium grade* is best for removing the stock, and a fine stone for
finishing the cutting edge. An oil-stone should not be used dry; the
face must be kept free from glaze. If there are deep depressions or
marks in the stone it should be faced off on a wet grindstone.

Fluted Chucking Reamers. The same general instructions given
for making fluted hand reamers are applicable to thb form, except
that the shank may be finished to size before the reamer is hard-
ened, unless the shank is to fit a collet or is to be held in a chuck.

Fig. 53.

m Showing Method of Grinding
ler for Clearance

TOOL-MAKING

The regular jobbing reamer used in the lathe is shown in
Fig».54; the form for the chucking lathe or drill press, where the shank
is held in a collet or a chuck, b shown in Fig. 55. When making the
latter style of reamer, B may be left .010 to .015 inch above size to
allow for grinding. The portion C may be finished to size, and the
dimension of the cutting part of the reamer stamped on it as shown;
if the reamer is made for special work and is to be used on no other,
the name of the piece or operation for which it is intended should also
be stamped.

On account of the uncertainty of a reamer cutting exactly to
size when used in a lathe, chucking reamers are frequently made

Fig. 54. Rose Fluted Chuddog Reamer
Courtety of Union Tu>i$t DriU Company, Athol,' Ma$taehiueU$

somewhat under size. Standard hand reamers are used for fiaishing.
The amount of stock left for the hand reamer varies. Some tool-
makers consider .005 inch the proper amount for all reamers up to 3
inches in diameter; while others think that for 1 inch or less diameter,
.004 inch is right, and that for sizes from Ifj inches to 2 inches,

Fig. 55. Chuckiog Reamer withlStraight Shank for Screw or ChuokiDg Marbioes

.007 inch should be allowed. For reamers larger than 2 inches in
diameter, an allowance of .010 inch should be made. The exact
amount necessary for finishing with hand reamers depends on the
nature of the work and the stock opei%tted on. Fluted chucking
reamers are made with either straight or spiral flutes.

When a reamer is used in a screw machine or a turret lathe, on
work where accuracy and straightness of hole are essential » it should
be held in some form of special holder, which allows it to locate itself
properly as to alignment. These holders will be described later.

Rose Reamers^ This form of reamer has its cutting edges only
on the end, the grooves being cut the entire length of body to reduce

TOOL-MAKING

the amount of frictional bearing surface and to furnish a channel
to conduct the lubricant to the cutting lips. In case there are blow-
holes or other imperfections in the material being operated on, this
reamer will cut a more nearly parallel hole than the fluted chucking
reamer.

Fig. 56 shows the ordinary form of rose chucking reamer. The
shank is turned to finish size; if it is to fit a holder, it is left slightly
larger and turned cr ground to size after hardening. The body
b turned .015 to .020 mch above finish size and the flutes cut; the
size is stamped as shown, and the reamer hardened a little above the
body. It is customary, when grinding a rose reamer, to make it a

Fig. 56. Rose Chucking Reamer with Straight Shank for Screw or

Chucking Machines

Courtesy of Union Tvoist Drill Company, Athol, Massachu$ett$

trifle smaller on the end of the body next to the shank — a taper of
ttH inch in the length of the cutting part gives good results.

Small rose reamers can be made of drill rod, which runs very
true to size, if ordered by the decimal equivalent rather than by the

Fig. 57. Small Reamer "Necked Down"

drill gage number, or in terms of common fractions. For instance,
if drill rod is wanted of a size corresponding to No. 1 Brown and
Sharpe drill gage, the size will be much more accurate if ordered as
.228 inch diameter, rather than by the gage.

The drill rod may be sawed to length, put in the lathe chuck,
and cornered for the cutting lips. When making small reamers that
are not to be ground to size after hardening, it is advisable to "neck
them down" back of the cutting edge, as shown in Fig. 57. The drill
rod often swells or expands at a point where the hardening ends; and
by necking down and hardening into the necking, this difficulty is
overcome.

TOOL-MAKING

Making Flvies, Small rose reamers may be given three cutting
edges. The fli^es may be filed with a three-square or a round-edge
file. If a three-square file is used, a groove of the form shown in
Fig. 57 may be made. This has a tendency to push the chips ahead
when cutting, while a groove filed with a round-edge file, if it is of a

Fig. 58. Reamer with Rigbt^Hsad Helix

spiral form, will draw the chips back into the flute, provided it is a
right-hand helix, as shown in Fig. 58.

Grinding. Rose reamers intended for reaming holes of exact
size must be ground to correct dimensions after hardening, but small
reamers intended for reaming holes where exactness of size is not
essential may be made to size before hardening, and the cutting
edges backed off with a file for clearance. If reamers are ground on
the circumference for size, the lips or cutting edges should be given
clearance by grinding. After grinding, the corners of the cutting
edges next to the body of the reamer, as shown at the right end of
Fig. 56, should be rounded by oil-stoning.

Single-Lipped Reamers. A single-lipped reamer is very useful for
reaming a straight hole. When the nature of the hole or the condi-
tion of the stock would cause the ordinary forms to run, the single-
lipped reamer will cut a straight hole if started right. Having but one
cutting lip, its action is similar to that of a boring tool used for inter-

Fig. 59. SiDgle-Lipped Reamer

nal turning in the lathe, and as a large 'proportion of the body 'of the
reamer acts as a guide, it must cut a straight hole. Fig. 59 shows
two views of this form of reamer.

Steel for this tool should be sufficiently large to allow the decar-
bonized surface to be entirely removed. After a roughing chip has

TOOL-MAKING 53

been taken — ^leaving ,the piece about ^ inch above finish size — ^the
stock should be annealed, and the portions A and B turned to a size
that allows for grinding. C may be finished to dimensions given,
and the size stamped as shown.

MiUing. The reamer is now ready for milling. Thb should be
done with the reamer in the centers in the milling machine, using a
shank mill or a small milling cutter on an arbor. The depth of the
cut should be about one-third the diameter of the reamer; for large
reamers, it may be somewhat deeper. After the milling, the face
may be smoothed with a fine file, and the end and cutting lip
backed off for clearance, as shown in Fig. 59 at D and E,

Hardening. When hardening, the end A should be heated to a
low red and dipped in the bath about one-half an inch up on the
necked portion C The temper may be drawn to a light straw.
A and B are now ready for grinding. If the grinder has no provi-
sion for the running of water on the work, care should be used not
to heat the reamer, as it is likely to spring.

Three- and Four-Lipped Roughing Reamers. These are used
to advantage in chucking machines, for enlarging cored holes or holes

Fig. 00. Three-Lipped Reamer

that have been drilled smaller than the required size. Large holes
in solid stock are often made below size, as most manufacturers
consider it more economical to use a smaller drill and a roughing
reamer to bring them to proper size for the final reamer. Fig. 60,
shows a reamer of this description.

The instructions already given for making the various reamers
may be followed for this form, with the exception of cutting the
grooves, which should be of a sufficient size to hold the chips. The
small groove cut in the center of the lands is to feed oil to the cutting
edges when cutting steel. When cast iron is the material to be
operated on, the grooves are cut straight and the oil groove omitted.

54 TOOL-MAKINO

If a finish reamer is to be used in sizing the holes, it is customary to
make the roughing reamer ^ inch smaller than finish size. On
|iccount of the rough usage, great care should be exercised in harden-
ing. While satisfactory results may be obtained by heating them to
% low red, plunging them into a bath of brine, and drawing the
temper to a light straw, the tools will do a great deal more if they
are. pack hardened.

Insertcd-Blade Reamers. The particular advantage of solid
reamers with inserted teeth is that, when worn, new blades may be

Fig. 61. lusertcd-Dladc Reamer with SccUoa Showio^; Method of Inserting Blades

put in at a cost much less than that of a new solid reamer. Inserted-
blade reamers are usually made in such a manner that the size can
be altered; in such cases they are termed expanding reamers. A sim-
ple form is shown in Fig. 61. The slots for the blades are milled
somewhat deeper at the front end than at the end toward the shank;
they are also somewhat wider at the bottom than at the top. The
first is accomplished by depressing the spiral head a trifle; while the
latter is done by first milling the slots with a cutter a little narrower

than the top of the slot wanted, then turning the
spiral head enough to produce the desired angle
on one side of the slot, as shown at A in Fig. 62.
The object in making the slot deeper at the front
end is that the blades, as they become dulled,
and consequently cut small, may be driven farther
Fig. 62. Form of Slot iuto thc body. As the slot is shallower, the blade

for Inserted Blade • # i ^^ • . i ^i • • •^

IS forced out as it advances, thus mcreasmg its
diameter; it may then be sharpened by grinding to size. The side of
the slot is cut at an angle to hold the blade solidly and prevent any
tendency it might have to draw away from its seating when the reamer
is cutting. The body of the reamer is not hardened; the blades are
machined to size, hardened, driven into place, and ground to size.
If the reamer is of the form known as fluted reamer, the teeth may be
backed off for clearance as already described.

TOOL-MAKING

£5

Adjustable Reamers. These are made in a form that allows
them to be adjusted to a varying size of parts of machines where
interchangeability is not essential. Fig. 63 shows the cheapest type
of adjustable reamer, one sometimes objected to because it does

i^=

Fig. 63. Adjustable Reamer

not expand or contract uniformly its entire length; for ordinary
work, however, it is very satisfactory, if used for a limited range
of sizes.

Stock should be selected at least ^ inch larger than finish size.
After carefully centering and squaring the ends, a chip should be
turned the entire length of the piece, which is then drilled, and
the taper hole reamed for the expansion plug. When drilling the
outer end, the blank should run in the steady rest; the hole in the
shank end should be drilled to the proper depth with a tool ^ inch
larger than the straight stem of the expansion plug. The end should
be chamfered to a 60-degree angle, to run on the lathe center when
turning and grinding. The piece may be reversed and the opposite
end drilled and reamed with a taper reamer; this end should be

^m^^mm^i^^^^^^^^^^^^^m^^^cm^^z^wy^.

Fig. 04. Blank for Adjustable Reamer Drilled aad Reamed

chamfered also to a 60-degree angle> Fig. 64 shows a sectional view
of the blank drilled and reamed and the ends of the hole beveled.

The reamer should now be turned .020 to .025 inch above finish
sizes on A and 5, while C and Z), Fig. 63, are turned to finish sizes,
and the size stamped at C The end E should be milled square for
a wrench, the grooves milled, and the reamer split, in order that the

TOOL-MAKING

TABLE III
Data of Shell Reamers

DUMBTH

an.)

Lbhotb
(in.)

8i» or HoLB

(in.)

ToKoun Suyr |

Width
(in.)

Depth
(in.)

1 toH
lAtolf
lHto2
2^ to 2}

2i
3

1
li

size may be altered with the expansion plug. To split the reamer, a
metal slitting saw of the required thickness — usually rfg inch —
should be used. The saw cut should not extend to the end of the
reamer, but a small portion should be left solid to prevent the reamer
from springing when hardening. .The circular saw leaves a cut at
the end of the shape shown in Fig. 65, which is extremely difficult to
part after hardening. In order that the thin partition of stock may
be easily severed with an emery wheel, the slot may be finished, as
shown in Fig. 66, with a hand hack saw.

The expansion rod 7, Fig. 63, should be turned to fit the taper
in the reamer, the straight end being ^^ inch smaller than the hole

running through the reamer, and threaded on the
end for a nut to be used in drawing the rod into
the reamer. The collar shown at F and H should
have a taper hole fitted to the tapered end of the
reamer. The outside diameter of the collar should
be a trifle smaller than the hole to be reamed.
The collar, when forced on to the end of the
reamer, holds the latter in place. In order to increase the size of
the reamer, the collar may be driven back a trifle and the rod

drawn in by means of the nut.

After the reamer is hardened and tempered,
the thin partitions left at the ends of the slots
may be ground away with a beveled emery
wheel, the rod inserted, the collar forced upon
the end, the reamer ground to size, and the teeth
backed off for clearance.
Shell Reamers. As a matter of economy, the larger sizes of
re^m^rs are sometimes made in the form of shell reamers, as shown

SI. 65. Form of Cut
■de by Circular Saw

Fie. M. Fonn of Cut
Mwie by Hand Saw

TOOL-MAKING 57

in Fig3. G7 and G8. Aa several reamers may be used on the same
arbor, there is a considerable saving in cost of material.

Table III gives the size aod length of shell reamers from 1 inch
to 3 inches in diameter, together with the size of holes, and width
and depth of tongue slot.

After drilling a, hole -^ inch smaller than finish size, the blank
should be placed on a mandrel, and a heavy chip taken to remove all
the original surface. The drill is annealed, and then placed in a
chuck on Ihe lathe and the hole bored .005-inch smaller than finish
size. After being put on a mandrel, the ends should be faced to
length and the outside diameter turned, leaving .010 to .015 inch on
the cutting part for grinding. The balance at the reamer should be
turned to size. If it is to l>e a rose reamer, the edge should he cham-
fered the proper amount.

Cvtlmg Slot. The reamer should be held in a chuck on the
spiral head spindle in the milling machine, and the tongue slot cut.

In order to get the slot central with the outside of the reamer, a cut-
ter somewhat narrower than the desired slot should be used, which
should be set as centrally as possible by measurement, a cut taken,
the spiral head turned one-half way round, and another cut taken;
the width of the slot should be measured, and the saddle of the
machine moved by means of the graduated adjusting screw one-
half the amount necessary to make the slot of the right width. The
reamer may be placed on a mandrel, between centers on the milling
machine, and the flutes cut.

Hardening. The reamer should be heated for hardening in
some receptacle, in order tiiat the fire may not come in direct contact
with it. When it reaches a low uniform red heat, it may be placed
on a wire hook, plunged into the bath and worked up and down

58 TOOL-MAKING

rapidly until all trace of red has disappeared, and should be left in
the bath until cold. When cold, it may be heated to prevent
cracking from internal strains. If it is to be a rose reamer, it may be
left dead hard; if it is to be a fluted reamer, the temper should be
drawn to a straw color. The hole should be ground to fit the shank
on which it b to be used, or to fit a plug gage, if there b one for the
purpose. The reamer may then be placed on a mandrel and ground
according to the general directions given for grinding reamers.

The holes in shell reamers are sometimes made tapering — the
end of the arbor being made of a corresponding taper — to avoid the
necessity of grinding the holes, as any slight change in the size,
resulting from hardening, would be compensated for by the taper hole.

Arbors for SheU Reamers. These are made as shown in Fig. 69.
The shank B and the end A to receive the reamer, are made in one
piece. The collar C having two tongues to engage in the slots in the
reamer, b made of tool steel; the hole b made of a size that allows it
to slide over A. When in position, a hole b drilled through both
collar and arbor and the pin D driven in.

When making the collar, the hole b drilled and reamed; the col-
lar, is placed on a mandrel, the ends faced to length, and the collar

Fig. 69. Typiosl Arbor for Shell Raamera

turned to proper diameter. It b then removed from the mandrel,
and the tongues are milled. While thb b being done, the collar b
held in the chuck on the spindle of the spiral head, and a side milling
cutter b used. One side b milled, the spiral-head spindle turned
one-half revolution, and the opposite side milled; the thickness is
measured, and the saddle moved enough to bring the tongues to the
required thickness, when the finbh cut b taken on each side.
After putting on the arbor and drilling the pinhole, the collar is
removed and spring-tempered. It may now be placed on the arbor,
and the pin driven in place.

When the shell reamer b made with a taper hole, the arbor b made
with the end ^1 of a corresponding taper. Otherwise the construction
would be the same as for shell reamers having straight holes.

TOOL-MAKING

TAPER REAMERS

If a taper reamer is intended for finbhing a hole, the same gen-
eral instractions for making fluted hand reamers may be followed
except that instead of being straight, the body or cutting part is
tapered.

Roughing Taper Reamers* These are frequently made in the
form of a stepped reamer, or it might be called a mvUiple counter'
bore, sauce each step acts as a pilot for the next larger st^, Fig. 70.

FSg. 70. Boughing Tvpu ReAmor .

.The steps A are turned straight, each one correspondingly larger
than the preceding. The cutting is done at the end of the step, B,
which must be given clearance; this is ordinarily done with a file.
The reamer may have four cutting edges, which should be cut with
a milling cutter intended for milling the flutes of reamers. The
number of the cutter selected will depend on the form «nd the
amoimt of taper of the reamers. It is advisable to neck down into
the reamer jb hich at the end of each step. This may be done
with a round-nosed tool, or a cutting-off tool having its comers
slightly rounded. The necking facilitates the filing of the cutting
edges, and also allows the emery wheel to traverse the entire length
of each step when grinding to size after hardening.

Roughing reamers are sometimes made of the form shown in
Fig. 71. The left-hand thread, cut the entire length of the cutting

Fig. 71. Roughing Rajuner with Short Steps for Breaking up the Chipe
Courtesy of Union Tvitt DriU Company, Atholt MtutackuseUa

portion, breaks the chips into short lengths, and greatly increases the
cutting qualities. After turning the tapered part to a siate that
allows for grinding, the lathe may be geared to cut a four-pitch

TOOL-MAKING

thread. The threading tool should be about ^inch thick at the
cutting point, and have suffident clearance to prevent the heel from
dragging when the tool is cutting. The comers should be slightly
rounded in order to reduce the tendency to crack when the reamer
b hardened. The thread should be cut to a depth of from A to A
inch. After threading^ the flutes may be cut, the reamer hardened,
and the temper drawn to a light straw.

When grinding a taper reamer, the proper clearance is given to
the tooth for a distance of ^ inch back from the cutting edge; the
balance of the tooth b given a greater amount of clearance, as shown
in Fig. 71.*

FORMED REAMERS

These are used for holes of an irregular shape, or rather of a
shape neither straight nor tapering: They are used chiefly by gun-
makers in reaming the end of the gun barrel for the shell, and are
termed, when used for thb class of work, chambering reamers.

Chambering Reamers. These have a sleeve on one end as
shown at A^ Fig. 72. Thb sleeve b a nice running fit on a pilot, and

Fie. 72. Chambered Reamer for Gun Barreb with Sleeve Shown at A

also fits closely in the hole in a gun barrel. Teeth are cut on the end
next to the cutting portion of the reamer. When the reamer is cut^
ting, the sleeve does not revolve in the barrel, but the pilot turns in
it. When the reamer is drawn out of the barrel, the semicircular
slot at the end engages with the pin passing through the pilot, and
the sleeve revolves and cuts away any burr that may have been
thrown up when the reamer was cutting, thus preventing the burr
from tearing the inside of the barrel.

It b essential that the stock be rough-turned a little aboye
finbh size and then annealed. As reamers of thb form must be
accurate in size and shape, it is customary to use a gage; thb b
generally a piece of steel in which a hole of the proper form has been
Teamed, and the stock cut away on one side, so that a trifle more

TOOL-MAKING

than one-half -of the hole is left, as shown in Fig. 73. To make the
reamer blank fit the gage, the operator must understand the use of
hand-turning tools, as most shapes must be made with these tools.
CvtHng Teeth, The teeth must be cut with a milling cutter of
small diameter, following the different shapes of the reamer in order

^^=^

Fig. 73. Gage Used for Formed Reamer

that the top of the land may be of as uniform a width as possible.
After cutting, the teeth may be backed off for clearance with a file,
care being taken not to remove any stock at the cutting edge.

Hardening, When hardening, the reamer should be heated
very carefully in a tube imtil it is of a low uniform red heat; it should
then be plunged into a bath of lukewarm brine. It may be bright-
ened and the temper drawn to a light straw. After hardening, it
should be tried in the gage, and any high spots removed by oil-
stoning.

Grinding. If a large number of reamers of one form are to be
made, the grindmg machine may be rigged with a form which makes
it possible to grind many of the shapes in common use. It is found
quite impracticable, however, to grind some shapes, and conse-
quently the method just described of fitting before hardening

Fig. 74. Square Reamer for Finishing Long Bote

must be adopted. Excellent results are obtained with the pack-
hardening process.

Square Reamers. Reamers used for finishing a long hole that
must be very smooth, are often made of the form shown in Fig. 74.
This reamer is drawn through the hole by means of the shank B, tlie

62 TOOL-MAKING

cutting portion being at ^1. It should cut but a very small amount
at each passage through the hole. A piece of hardwood is placed
on one side of the reamer, as shown at C. After the reamer has
passed once through the hole, a piece of tissue paper is placed between
the reamer and the chip, and another cut is taken, this being repeated
each time the reamer passes through. Several passages of the
reamer and repeated blocking between the chip and reamer, result
in a beautifully finished hole of the desired size.

Hardening Form Reamers. Long reamers and similar tools,
made from high-speed steel, are very likely to warp and bend imless
heated for hardening in a vertical position. To^ accomplish this,
they should be suspended by their shanks in a specially designed
vertical furnace, as shown in Fig. 22. The shanks project through
holes in the top of the furnace, and are held by suitable holders.
As the temperature in high-speed furnaces is very great, the reamers
should be pre-heated to a low red before being placed in the furnace.
This pre-heating should be done in an open fire, or in a furnace where
the process can be carried on slowly.

Reamers should not be heated to so high a temperature as tools
that have no projectmg portions. The limit of temperature for
tools of thb class is about 2300^ F. When this temperature is
reached, the reamers should be plimged vertically into a bath of cot-
tonseed oil and worked vertically until they have cooled below a red.

As the process of hardening makes the tool extremely brittle,
it is necessary to draw the temper of most forms of reamers to a full
straw color (460® F.). If the reamer is slender, and is to be sub-
jected to considerable strain, the temper may be drawn to 480® F.
or 600* F. (brown color).

Reamer Holders. On account of the uncertainty of exact align-
ment of every part of a screw machine or turret lathe, it is desirable
to use a holder that allows each part properly to align itself. The
form shown in Fig. 75 is conunon and gives good results. It consists
of the body A, which has a hole drilled uid reamed its. entire length.
The hole must be somewhat larger than the shank of the reamer,
^ inch bemg considered sufficient. The center By of tool steel,
which has the point wtXy hardened should be, after hardening, .010
to .015 inch larger than the hole in the holder; the point ^ould
be ground to a 60-degree angle, and the straight part ground to a

TOOL-MAKING

fordng fit in the holder. After being forced to position, a hole is
drilled through the holder and center, and the pin C driven in to
keep the center from bemg pressed back by the reamer when in

Fig. 7S. Typioal Rcmmt HoUtor

operation. A pin should be put through the holder at D and a hole
-fi inch larger than the pin should be put through the reamer shank
at this point; this pin is simply to prevent the reamer from turning
when it <x>mes in contact with the work. The coil springs EE hold
the reamer in position to enter the hole, and the proper tension is
l^ven by means of the screws FF.

ARBORS

TookSteel Mandrels; The ordinary taper arbor, known as the
mandrel, is in common use in most machine shops. Up to and
including a diameter of 1) indies, mandrels are made of tool steel,
hardened all ovot and groimd to size. Some tool-makers advocate
making all mandrels up to a diameter of 4 inches in this way; others
Iffefer hardening the ends BB, Fig. 76, leaving the center A soft,
wlule others maintain that for mandreb above 1) indies in diameter,
machine steel is most satisfactory if thoroughly casehardened.

When makmg mandrels of tool steel that are to be hardened the
entire length, it is not necessary to use the best quality of steel; a

Itf. 76. Oidiiuury Fonn <tf Tool-Steel Mufdrel

lower grade will do, if it hardens wdl. Select stock some^^iat
larger than finish diameter, say ^ inch for sizes up to ) inch, \ inch
fpr sizes up to 1 inch, ^ inch for sizes up to 1| inches, and \ inch for

TOOL-MAKING

larger sizes. Take a chip off the outside, sufficiently heavy to
remove all scale, yet leave A inch for a finish cut on sizes up to
J inch, and correspondmgly more for the larger sizes. The man-
drel should now be annealed, preferably in the annealing box.
The ends should be countersunk deeper in mandrels than in tools
where the centers are not used after they are completed. In order
that the centers may not be mutilated when driven in or out of the
work, they should have an extra countersink, as at il in Fig. 77, or
else the cut should be recessed as &tBm Fig. 78. This operation is
known as cupping the centers.

The ends BB, Fig. 76, should be turned to size (standard dimen-
sions up to 1-inch diameter are given in Table IV), the corners
slightly rounded, and the flat spots for the dog screw milled or
planed. The body of the mandrel should be turned somewhat

fig. 77. Extra Countersink on Mandrel

Fig. 78. Recesaed Center on Mandrel

larger than finish size; those smaller than \ inch should have an
allowance of .015 inch; from J to 1 inch, an allowance of .020 to .025
inch; over 1 inch an allowance of .025 to .030 inch. As the length
of a mandrel larger than 2 inches in diameter does not increase in
proportion with the diameter, the amount given will generally be
sufficient if proper care is used when hardening. The size should
be stamped on the end next to the laTge end of the body.

Before hardening, the centers should be re-countersunk to true
them; for this operation, it is best to use a special countersink having
an angle of 59 degrees instead of the regular 60-degree tool, as the
former facilitates the lapping of the centers to a 60-degree angle
after hardening. This is necessary on account of the unequal
amount of grinding caused by the shape of the countersink.

Hardening, If a blacksmith's forge must be used when heating
the mandrel for hardening, the fire should be large enough to heat
the piece evenly; it is advbable to heat it in a tube. Results more

TOOL-MAKING

TABLE IV
Dimensions of Mandrels

(Diameters up to 1 inch)

j(r^

)l*~l

"Wi

"^"^^^^

' L

::5

\^jr-

•

(in.)

■
■
•

5
51

5}
61

6
6J

1
lA

6
6

nearly uniform can be obtained from a muffle furnace than from the
open fire. In either case the piece should be turned frequently, to
insure an even heat.

Best results follow if the kind of bath shown in Fig. 79 is used.
Perforated pipes, which may be moved toward the center for small
pieces, are used. These pipes — six in number — extend up the sides
as shown. Small holes are drilled in them in such location that the
water is projected toward the center of the bath. The bath is also
provided with a pipe which throws a jet of water upward from the
bottom, thus insuring th^ hardening of the center at the lower end
of the mandrel. A stream must also be provided at the top as
shown, to insure the hardening of the upper center hole.

The form of tongs shown at the left of bath should be used, as
with these the water has free access to the upper center, which
would not be the case with ordinary tongs. If a still bath is used,
it should be of strong brine, and the mandrel should be worked up

M TOOHtfAKING

and down tidenUy to insure the liquid coming in cootact with both

A mandrel of a diameter latger than 1 inch should be removed

from the bath as soon aa it ceases "aingiiig", end held in a tank of

oil until cold. The ends should be brightened and drawn to a deep

straw color, to toughen them so that they will not break or chip oS

whea driven. Mandrels smaller than ] inch should have the temper

drawn to a light straw color the entire length of the body. After

hardening, the body of the mandrel should be cleaiied with a coarse

emery cloth to remove the scale or

grease which would glaze the

» emery wheel.

Finiihing CenUr*. The man-
drel should then be tested between
centers to see if it has q)rung men
than will grind out before it
reaches the proper size. The cen-
ters should now be lapped, to
insure proper shape and align-
ment. The lap may be a piece
of copper of the proper shape —
60 degrees — charged with diamond
dust or emery. After lappnng,
Fi(. T>. epMJi Typa cS Biib lor the Centers should be thoroughly
cleaned with benzine. (When
iisini^ htnmne, do not allow it to get near a Same of any kind.)

Grindrng. Examine very carefully the condition of the centers of
the grinder, as the trueness of the mandrel depends in a great meas-
ure on their condition. A mandrel may be ground in a lathe having
a grinding attachment, or in any universal grinder. Better results
can be obtained, however, with some form of grinder havmg a
stream of water playing on the work to prevent heating, as heat is
likely to spring the piece, especially if it does not run true, and th)(s
to make the grinding heavier on one ^de than on the other. If a
dry grinder.must be used, do not force the work fast enough to heat
the piece. The mandrel should be ground to within about .005
inch of size with a coarse wheel free from glaze, and then fiolahed
with a Gine wheel.

TOOL-MAKING 67

Tapering. The amount of taper varies. Most manufacturers
prefer a .0005-inch taper per inch of length, while others make man-
drels with a .001 -inch taper, maintaining that if a piece having a long
hole is to be held on any taper mandrel, it will not fit at the part
nearest the small end of the mandrel, and that consequently the
turned surface will not be true with the hole; for such work, they say,
a mandrel should be made for the job, having a body nearly or quite
straight. They advise that the mandrel be made to taper .001 inch
for every inch of length in order that it may be adapted to a greater
range of work. However, a .0005-inch taper seems better for
most work.

Mandrels with Hardened Ends. When making a mandrel the
ends of which are to be hard, and the body soft, the general instructions
given for hardening mandrels hold, except that a larger amount of
stock should be left on the body. The ends should be hardened
for a distance that insures the centers being hard; this can be
rccomplished by heating one end at a time to a red heat, and
inverting under a faucet of running water. As the center is
uppermost, the water can readily enter it, forcing the steam away.
After drawing the temper of the ends and lapping the centers,
the body may be turned and filed to size. The centers of the lathe
should be carefully*' trued before starting this operation. If the
bady of the mandrel is left .008 inch to .010 inch larger after
turning, and then ground to size, the results will be surer; but with
extreme care a very satisfactory job may be done by the method
dciiscribed.

Machine Steel Mandrels. With the exception of hardening,
the instructions given for making mandrels of tool steel apply to
those made of machine steel. Machine steel mandrels must be
casehardened. The work should be run in the fire from 7 to 10
hours after the box is red hot throughout; then it' should be dipped
into a bath having a jet of water coming up from the bottom, to force
the steam away from the work and avoid soft spots. It is not neces-
sary to draw the temper, as the hardening does not extend far below
the surface.

Expanding Mandrels. There are several forms of expanding
mandrels in common use. One form has a sleeve with a taper hole,
fitting on a mandrel with a corresponding taper; the sleeve is split

TOOL-MAKING

Fig. 80. Expanding Mandrel

to allow it to expand as it is forced on the mandrel. This form b
shown in Fig. 80.

It is not advisable to give the mandrel very much taper, because
a heavy cut, with the pressure toward the small end, would crowd the

sleeve toward that end and
release the work. Ordinarily
a taper of J inch to the foot
will give good results.

It is obvious that the
range of adjustment for such
a sleeve is small, but sleeves of different diameters may be fitted
to the same piandrel, the thickness of wall being varied to give the
desired size. The diameter of the sleeve should be such that the
work may enter without forcing, the tightening being accomplished

byiorcing or driving the
sleeve toward the large
end of the mandrel.

If a sleeve is needed
for a special sized hole,
and is to be used but a
few times and through a
limited range of sizes, it may be made of cast iron. A hole, corre-
sponding in size and taper to its mandrel, is bored so as to allow the
small end of the mandrel to go through and be flush with the end
of the sleeve. The sleeve should be forced on the mandrel and turned

to size; the outside diam-
eter should fit the hole
in the piece to be ma-
chined when the sleeve is
at the small end. In
order that the sleeve may
be expanded, it is split as
shown in Fig. 81. Thb
should be done in the milling machine, the sleeve being held by the
ends in the vise, and the cut made with a metal slitting saw.

When the sleeves are intended for permanent equipment, it is
good practice to make them of either machine steel or tool steel;
if of the former, they may be casehardened; if of the latter, they may

Fig. 81. Diagram Showing Method of Expanding
Mandrel Sleeve

Fig. 82. Method ol Splitting Sleeve for Unifonr
Expansion

TOOL-MAKING 69

be hardened and spring-tempered. In either case the hole should
be .010 inch small, and the outside diameter .020 to .025 inch large,
and ground to size after hardening. A method of splitting the sleeve
for an expansion more nearly uniform is shown in Fig. 82; small sizes
have four cuts for adjustment, while the larger sizes have six or eight.

On account of its peculiar construction, the sleeve shown in
Fig. 82 must be so held while grinding the hole that it will not spring.
^To do this, the sleeve may be placed in a hole in a collar and held
rigidly in position by several drops of solder. In order that the
solder ma^ stick, the outside of the sleeve must be brightened, -and
the metal heated until solder will melt on its surface. Care must
be exercised, as the surface of iron commences to oxidize at 430^ F.,
and soft solder melts at about 400^ F.; and as solder will not stick
to an oxidized surface, the metal must not be heated above 400
degrees. For this class of work always use soft solder, made by
melting together equal parts of tin and lead.

Many mechanics think it b impossible to solder cast iron, but
such is not the case. If soft solder is used and care is exercised in
heating, little or no trouble will be experienced.

When soldered secu^ly, the collar should be placed in the chuck
on the grinding machine, and the hole ground to the desired size,
after which it is heated to melt the solder, and the sleeve removed
from the collar. It can then be placed on the mandrel, and the
outside diameter ground to the proper size.

Eccentric Arbors. Arbors are made eccentric in order that the
outside of a piece of work may be made eccentric to the hole running
through it, as shown in Fig. 83.

When making an eccentric arbor, the general directions given
tor making mandrels
should be followed,
except that the centers
must be rather small. The
mandrel should be placed
in a V-block or in a pair

of centers; and by means Pig. 83. P»rt Section and End view of Piece of Work
• _> ,.> with Eccentric Hole

of a surface gage, tbe

needle of which has been set at the exact height of the center, aline

may be drawn, as shown in Fig. 84, across each end of the mandrel.

TOOL-MAKING

The mandrel may now be turned so that the line will be vertical; the
pomt of the surface-gage may be raised to give the required amount
of eccentricity, and a line, as shown m Fig. 85, scribed on each end.
The ends should be prickpunched where the lines intersect, and

drilled and countersunk at this
point.

After hardening, both pairs

of centers should be lapped to

shape. The centers, marked A A ,

Fig. 86, must be used when

^!iaJ^'JSc'^''??r iS^tiSrSln^^ «^^^ *^« "mandrel to size, or

anc t
Ceni

ter

Center

in tiuning work which is to be
concentric with the hole, while the centers BB are used when turn-
ing the eccentric parts.

Use of Jig for Accurate Work. This method of laying off and
drilling the eccentric center, may not give the necessary accuracy.

Fig. 86. Part Section of Mandrel with Eccentric Centers Located

and if it does not a jig must be used in drilling the center holes. A
suitable jig is shown in Fig. 87. The ends of the arbor must be
turned to fit the hole A in the jig, which b a collar having a straight
hole through it. A piece of steel, which is a forcing fit in this hole,

has a hole the size of the
centering drill, laid off with
the proper amount of eccen-
tricity. Thb piece of steel
is forced to the center of the
collar, at B. A straight line
should be drawn across the
collar and down the beveled
edges, as shown at C, A line
should now be scribed the entire length of the mandrel, which
should be set to match the line on the jig. The. jig is secured in
its proper position by means of the set screws.

W ^

Fig. 87. Jig for Locating Centers

TOOL-MAKING

Use of Mandrels vrith Two Centers. For machining a cylin-
drical piece which has a hole through it to receive an arbor, and the
faces of which are not parallel, Fig. 88, it is well to use a mandrel
having two sets of centers, Fig. 89, A A being the regular centers,
while the eccentric centers,
BB, should be equidbtant
from the regular centers, but
on opposite sides.

Milling-Machine Arbors.
Arbors for milling machines
should be made from steel
strong enough to resist with-
out twisting or springing, the
strain caused by tightening the nut. When a limited number of
arbors are made, tool steel is generally used; but for many milling
machines, necessitating a great many arbors, a lower priced steel
having the necessary stiffness b selected.

Fit. S8. Cylindar with Faces not Parallel

Fie. 89. Mandrel Showing Two Seta of Centera

After centering and squaring the ends, a chip is turned the
entire length of the piece, to remove all the outer surface. The
ends D and C, Fig. 90, are next turned to size, and the tenon milled
to the desired dimensions. In milling for the tenon, the arbor

Fig. 90. MilUnc-MachineAibor

should be held between centers, and the cutting done With an end
mill of the form shown in Fig. 91, the circumference of the cutter
leaving the proper shape at the end of the tenon. The centers
should be hardened, and the temper drawn to a straw color. If

72 TOOL-MAKING

the projection on the end of the arbor at C, Fig. 90, is to be run in a)
socket in the tail block of a milling machine, it must be hardened
the entire length, in which case the thread for the nut should be cut
before the end is hardened.

If a lathe having a taper attachment is used, there is no particu-
lar method of procedure other than roughing the arbor nearly to size
before either the taper or the straight end is finished. It will save
time, however, if the straight end A, Fig. 90, is roughed first, then
the taper B roughed and finished, after which the shoulder £, and
the straight part A, may be turned to size and finished. If the pro-
jection C b to run in a socket, it should be turned .010 or .015 inch

Fig. 91 Left-Hand Eod Mill
Courtesy of Union Twist Drill Company, Athol, Maaaaekutetta

above finish size, and ground to the proper dimensions. If it is
necessary to use a lathe having no taper attachment, the necessary
taper must be obtained by setting over the tailstock. In this case
it is better to turn and fit the taper first, for otherwise the centers
would become changed enough to throw the arbor out of true.

These instructions should be followed wherever a straight and
taper surface are to be turned on the same piece of work, in a lathe
having no means of turning tapers other than by setting over the
tailstock. Where extreme accuracy is required, it is advisaWe to
leave the straight and taper parts a few thousandths of an inch
above size, and to grind to size all over after the spline cut is taken.

Milling-machine arbors should have a spline slot cut the entire
length of the part that is to receive the cutters and this can best be
done in a shaper. Before putting the arbor in the shaper vise, a
hole should be drilled close to the shoulder into which the tool is to
run. The drill used should be about ifc inch larger in diameter than
the thickness of the splining tool, and the hole drilled a trifle deeper
than the slot to be cut. When the arbor is placed in the vise, a piece
of sheet brass or copper should be placed between the arbor and the
vise jaws to prevent bruising the arbor.

TOOL-MAKTUG 73

NtU». T3ie Dut ia usually made of machine steel, easehardened :
A bar of steel -ft inch larger than the finish size of the nut is selected,
and a piece ^ inch longer than finish length b cut ; it is then put in
a chuck on the lathe, the hole drilled, and the thread cut. If no tap
of the desired size b at hand, the thread may be chased; if a tap can
be obtained, the thread should be chased nearly to size and finished
vith the tap. Before being taken from the chuck, the end of the nut
should be faced, and the hole recessed to the depth of the thread for
a dbtance of two threads; after being removed from the chuck, it
should be placed on a threaded mandrel the threaded portion of
which fits the thread in the nut. The nut should be turned to size
and length, and the two opposite sides milled to receive the wrench
used in tightening. Fig.
92 gives two views of the
nut. It should be made
and casehardened before
the thread is cut on the
arbor, in order that the
thread may be made to fit
thenut. MiJling-machine .*^*^ i>uii.=tN>..(.rMiiimrM«tin.Aii»,
arbor nuts should fit the thread on the arbor in such a manner that
they may be turned the entire length of the thread without the aid
of a wrench, yet not be loose.

TAPS
Process of Making. Use of Screia Dies. When making t^ps
} inch in diameter and smaller, the threads are often cut with screw
dies, of which there are two styles. The form of screw plate shown
ial?ig. ^3 iitermei^ jam die plate. With this form the die b opened
to allow the wire to pass through, until it b even with the outmde
edge of the die, which is now forced into the wire by means of the
adjusting screw; the screw plate is revolved until a thread of the
desired length is cut. Thb operation b continued, the die bemg
closed a trifle each time, until the right size b obtained. The method
taken for gaging the correct size varies in dilTerent shops; if only one
tap b made, the tops of the threads are measured with a microm-
eter caliper; but for many taps of the same ^ze, such as for sewing
machines, guiia, and bicycles, a sissiTig die b used to give the

TOOL-MAiaNG

threads an exact size. The threads are cut to within a few thou-
sandths of an inch with the die plate, and finished with the sizing
die. One form of sizing die is shown in Fig. 94.

Where a great many taps of one size are cut, it is customary to
use several dies of different sizes, one of which, the finishing die, is

Fig. 93. Typical Jam Die Plate
Cowtety of Motm Tvritt DriU and Machine Company, New Bedford, Mauuchu»etU

always made adjustable. The roughing dies may be made solid or
adjustable, but the finishing must be adjustable for wear and for
the changing size of the taps. These dies are sometimes held in

separate holders of the

form shown in Fig. 94,

but a more convenient

form of holder is the

one shown in Fig. 95.

If all the dies are in one

holder, they are not

scattered around the shop. When many taps are made at a

time, the work can be done better and more cheaply if the wire

is held in a chuck in a lathe. The die plate should be placed

Fig. 94. Simple Form of Sixiog Die

Fig. 95. Form of Gang Die Holder

against a dnll pstd held in the tail spindle of the lathe, in order
to insure starting the threads true. The largest die should of
course be run on first, the second largest next, and so on to the
finish die.

TOOL-MAKING

Stoci:. For taps up to and including those i inch in diameter,
is customary to me a drill rod. The taps should be chamfered for a

distance of three or four threads, aa shown at A, Fig. 96, in order
tl»at the point may enter the drilled hole.

Taps larger than i inch are made from tool steel. Taps of J- to
i-inch diameter should be made of stock at least -^ inch large, Which
should be centered quite accurately with a small drill, because a
large center hole weakens the tap and increases the liability of its
cracking when hardened. After taking a chip sufficiently deep to

fla- BT. TiIMil(Su4Ti]». I«[l-T*perTap;Oiiur.Fl>i(Tip;Riglit-B«u>imiigTq>

remove all the outer coating, the tap should be box annealed, if

Tap Sets. Taps for general use around the shop are often made
in sets of three. The first tap to enter the hole b called-the taper tap,
because of the long chamfering op taper.'fhe second is known as

7fl TOOL-MAKING

the plug lap; this tap baa the first two or three end thieads cham-
fered, and U used when the screw b to go nearly to the bottom of
the tapped hole. The bottoming tap b used when the thread b to
go to the bottom of the hole; the end of thb tap U not chamfered,
Rg. 97.

Hand Taps. Hand taps are intended for tapping holes by
hand, and are usually made in seta «f three, as previously explamed.
After being annealed, the
shank should be turned to
size and the square end milled
for a wrench. The body
should now be turned to size,
and the thread cut. Before
I turning any of the parts to

size or starting to cut the thread, be sure that the centers of the
lathe are in good condition — the live center should run true, the
dead center should fit the center gage and be in good shape.

It b advisable to cut the tap slightly tapering, the thread being
from .0005 to .001 inch soialler at the end toward the shank. This
prevents the tap from binding wher.
slightly worn, yet does not taper enough
to affect tjie accuracy of the thread.
The thread tool should be an exact fit to
the gage, and pieced in the tool post so
that the top of the shank stands about
level. The top of the blade shown at A,
Fig. 98, should be ground parallel with
the top of the shank and the cutting
point should be set at the exact be^ht
of the point of the head center. Many
tool-makers consider it advisable to rough
the thread nearly to size with a single-
"" point tool, finishing it with a chaser

btld in the same holder. A chaser blade b shown in Fig. 99.

MiUing Flulea. After the thread b cut to size and the end
chamfered, the tap b ready to be grooved in the milling machine.
The tap is held between centers, and the grooves cut with a cutter
especially adapted to the ^ze and style of tap. While the grooves

TOOL-MAKING 77

are best cut with a milling-machine cutter, it is possible to cut them
in a planer or a shaper, using a tool of the proper shape. Great
care must be used not to stretch the tap by heavy chips, or by using
a dull tool.

The grooves cut in taps are ordinarily termed flutes. When
making taps for the market, it is usual to cut four flutes in all taps up
to and including those 2| inches in diameter. But when taps are
made in the shop where they are to be used, the number and shape
of the grooves depend on the nature of the intended work. Atap
that is to run through the work without any backing out can havq a
flute of a shape different from one that is to tap a deep hole in a piece
of steel where it is necessary to reverse the motion of the tap every
two or three revolutions to break the chip,
and also to allow the lubricant to reach the
cutting lips.

^liile all taps up to and including those
2J inches in diameter are usually given four
straight flutes, spiral flutes are sometimes
desirable, especially with small taps, for some
classes of work. With spiral flutes, it is ,, ,«« tu j- « r

*^ ' Fi«. 100. Threading Hole

generally necessary to cut a smaller number . ®"cutAw«j^ *
than with straight flutes, and, as taps are
not ground after hardening, , there is no objection to giving an
odd number of teeth, 'as in the case of a reamer. Three spiral
flutes are often cut.

If a tap one inch in diameter, having four flutes of the regulation
width, were used to tap tubing having thin walls, the tubing between
the lands would have a tendency to close into the flutes of the tap
and might break the tubing or the tap. In such "a case there should
be double the number of flutes. In order to provide enough lands to
hold the tubing in shape. If the hole to be tapped has part of its
circumference cut away, as shown in Fig. 100, more than four lands
are necessary. For general machine-shop work, however, four
flutes work well in hand taps up to and including those 2} inches in
diameter. For larger sizes, some tool-makers advocate six flutes;
others claim best results from taps having four flutes, regardless of
size. The class of work and the stock used in the individual shop
must determine this*

78 TOOL-MAKING

Forms of Fljites. The most commonly uaed form of flute is
that cut with aconvexmiUbgcutterformillinghalf-circlcaiFig. 101.
The sdvantsgea claimed for this form are (1) that the flutes are
deep enough to provide for the chips, and yet leave the lands as
strong as need be; and (2) that the form of the back of the land is
such that the chips cannot be wedged between the
land end the work when the motion of the tap is
reversed. The form of groove made with this cut-
ter is shown in Fig. 102. In order to support the
tap when starting to cut, and prevent cutting the
hole large at the outer end, hand taps have
their lands left wider, A, Fig. 102, than
the lands on machine taps. If the forms
of cutter illustrated in Fig. 101 or Fig. 103
are used, the width of lands as shown at A
may be one-fourth the diameter of the
tap. Fig. 104 shows a special fonn of
cutter. Itdoesnot make so deepa groove.
Fig. 105, IP proportion to the width, as a
tap and reamer cutter.

After cutting the grooves, the lands
should be backed off to give the tap cutting
edges; thb is usually done with a file.
Commence at the heel of the land A, Fig.

106; file the top of the land and graduatly approach the cutting edge,
makbig sure that no stock is removed st that portion — simply bring

TOOL-MAKING

it to a sharp edge. Enough should be filed
off the heel A to make it cut readily, yet not
enough 'tp cause it to chatter. The size and
number of threads per inch should be stamped
on tht: shank of the tap. IF it has a thread
differing from the one in general use In the
shop, that should also be- stamped on the
shank, as "U. S. S." if it is a United States
Standard thread.

Below are given the numbers of the cut-
ters For ditlerent diameters of taps when the
form shown in Fig. 104 is used:

Vo. 1 cut(«r cuu taps up Ut l-inch dumeter

No. 2 cutter cuti taps fpam A-iacb to i-inch diamelcr
Ko, 3 cutter cuti taps from A-toch to l-inch <tiamel«r
No. 4 cutter cuts tapa from iV'ich to i-uicb diameter
Ko. 6 cutter cuts tspa from H-''ieh to i-iocb diameter
No. 6 cutter cuts taps from H-'oe'' to ll-inch diameter
No. T cutler cuts taps from 1 A-inch *" 1 l-inch diameter
No. S cutter cuts t^>s Irom 1 ft-inch to 2 -inch diametFr Stdt by Bk

Hardening. If but a few taps are to be hardened at a time, it is
customary to beat them in a gas jet or an open fire of charcoal or
hard coal. It is advisable, however, to heat them gradually in a
tube. They should be plimged one at a time into the bath a little
above the threads, and worked up and down and around in the bath
to prevent soft spots. Excellent results Follow the use of the bath
shown in Fig. 79. Taps of l-inch diameter and smaller sliould be

left in the bath until cold; larger ones may be removed from the
bath as soon as the singing noise ceases, immediately plunged into
oil, and left until cold. For taps of less than l-inch diameter, the
citric acid bath will be found satisfactory; for large? taps, strong
brine is advbable

so TOOmAKINa

To have the tap retain as neitrly as possible its size
and correctness of pitch, use the. pack-hardening process.
Run taps ) inch in diameter and smaller for ) hour
after they are red hot; taps 1 to ] inch in diameter, 1
hour; taps 1 to ) inch in diameter, 1} hours; taps of a
' diameter larger than 1 inch, 2 hours. Harden in a bath
of raw Imseed oil.

Grinding. It is advisable to grind the flutes of the
taps with an emery whed of the proper shape in order to
brighten the surface so that the color will be readily seen
when drawing the temper. Grinding also sharpens the
cutting edges, and breaks the burrs that have been
thrown between the teeth when cutting the flutes. The
temper should be drawn to a full straw color. Much
more satisfactory results may be obttuned by heatbg the
taps in a kettle of oil, drawbg the temper to a point from
460* F. to 500° F., accordmg to the wze of the top and
the nature of the stock to be cut.

Machine Tq)s. As the name implies, machine taps
are intended for screw machines, tapping machines, and
lathes. They are held in chucks or collets by their
shanks, and are supported firmly. Consequently the
lands may be narrower than those of hand taps to make
them offer less surface to the work, thereby reducing the
amount of frictions! resistance. Also, they may be
rdieved between the teeth, by filing with a sharp-cor-
nered three-square file, commencing at the heel of the
tooth and filmg nearly to the cutting edge. It is not good
K,. 107. T«. practice to relieve the teeth very much, because chips
ah'inkf^ may be drawn between the work and the lands when
MiduDH backing out of the work. When tops are to be used
WiUu^fii in an automatic tapping machine without reverse
latBaintmm- motlon, thc shanks are left long as shown in Fig., 107, in
'rtiiJSl"' order that the nuts may pass over the thread and on to
the shank. When this is full, the top is token from the
machme and the nuta removed. This can be rcadiiy done, as they
will pass over the end of the shank.

If a top is to be used on nuto whose holes are punched to mx.

TOOL-HAEINa 81

mudi better results are obtained by using a tap with five flutes,
Fig. 108, instead of four. The uneven number of cutting edges

nf. IDS. Tv viUi Fin Fhitu

reduces the likelihood of an imperfectly tapped hole, while the extra
land furnishes additional support.

Taper Tq>s. When cutting tiie threads of a taper tap. Fig. 109,
it ia necessary to use a lathe having a taper attachment, as
the pitch of the threads is not correct if, the taper is obtained
1^ setting over the tailstock. Like machine taps, the teeth of a
taper tap must be relieved back of the cutting edge. In setting

. Typi™! T«i>M T»p

the threading tool for cutting taper taps, care ^ould be taken
that it is square with the axis of the tap, rather than square with
the taper sides.

Screw Die Hobs. Die hobs are finish taps for sizing the thread
lo-serew cutting dies. The several flutes are narrower than those of
an ordinary tap, and the lands are correspondingly wider. The tap
shown in Fig. 110 has eight flutes. The increased number and
broader lands support the tap while running through dies whose
clearance boles are drilled, in order to remove burrs thrown in the
threads when drilling. It b customary to give screw die hobs from
six to ten flutes.

When hobs are used for solid dies, they must be of enact Mze.
When intended for tapping adjustable dies, such as are ordinarily
used for cutting threads in screw machine work, the hobs are made

82 TOOL-MAKING

from .003 to .005 inch above the size of the screw to be cut. _ The
extra size gives relief to the threads of the die.

While it b generally considered advisable to run one or more taps
through a die before the hob, some tool-makers consider it better to

LKHTNINe

TT-rrrv »>T» » » »T» r .-

;"iv«

Fig. 110. Screw Die Hob

Cowiny «/ Wiley and Ru»»eU Manufaclurinc Company,
CreenfieU. AfataachtuetU

make a hob that will do all the cutting, claiming that no two taps can
be made and hardened so that the pitch will be exactly the same.
In such cases a hob is made that will cut a full thread by passing
through the die, Fig. 111.

Some manufacturers cut the thread tapering for about three-
quarters of its entire length, leaving the balance straight for use in
sizing the die. Others cut the thread straight and taper the outside
for three-quarters of its length. If the threads are cut tapering,
they must be relieved back of the cutting edges.

When hardening large hobs, those, say, 3 inches in diameter and
larger, it is a good plan to fill the threads with the mixture of charred
leather, flour, and salt, used for hardening twist drills. After this
dries, the taps may be heated and hardened. Best results follow
if they are hardened in a bath of lukewarm brine.

FiK 111. Hob lor Cutting Full Threads

Courtetif of S W Card Manufaetwring Company,

MautfiM, Ma*»achua«U*

Adjustable Taps. A solid tap made to cut to exact size,
having no leeway for wear, soon becomes too small. This fault
is overcome by making a tap that may be adjusted from time to
time. Another advantage of adjustable taps is that the holes

TOOL-MAKING

may be tapped to fit hardened acrewB, which vary in size because
of the hardening.

Probably the most common form of adjustable tap is the one
shown in Fig. 112. This tap is made in one piece, and then split. It

Fig. 112. Section of CommoD Form of Adjustmble Tap

has some means of adjustment whereby the tap can be expanded
or contracted through a limited range. This can be accomplished
by using a taper-bodied screw. The hole to receive the screw
should be drilled, tapped, and taper-reamed before the tap is turned
to size. The thread should then be cut, and the taper thread cut
on the end at A, There is less tendency to spring, when the tap is
hardened, if the projection shown in Fig. 113 is provided; this may
be ground off after the tap b hardened and tempered. When the
Eutes have been cut, the tap should be split in the milling machine
by using a metal slitting saw, the tap being held between centers.
It is split on two opposite sides, as shown at B, Fig. 112. The
splitting should not go to the end of the projection.

For hardening taps, pack hardening is best. If, however, this
method cannot be used, the tap should be heated very carefully in
a muffle furnace, or in a tube, the hole for the adjusting screw having
previously been plugged with fire
clay mixed with water to the
consistency of dough. When
heated to the proper degree, the
tap should be dipped into a bath
of lukewarm brine, and worked
up and down rapidly. After
hardening, it should be ground in the flutes, and the temper drawn
to a full straw color. The projection on the end may be ground
off, the taper screw inserted, and the locking, nut 5, Fig. 112,
screwed to place. This nut has a taper thread cut inside to corre-
spond with the thread on the tap at ^4. It will be found necessary

Fig. 113. Split Tap

M TOOL-MAKING

to cut the taper thread on the tap and in the nut, by means of the
taper attachment.

loMited-Blade Tqis. The first coat of an inserted-blade tap
may not be much less than that of a solid tap of the same size, yet
the comparative cheapness of new blades, which can be inserted in
the same body or holder when the first set becomes worn, makes this
form very valuable for taps larger than 1} inches in diameter. The
tap shown in Fig. 114 may also be used as an adjustable tap.
The shank or hdder A is made of machine steel, and the adjusting

collars C, are beveled on the inside at one end, at an angle coire-
sponding to the angle on Uie ends of the blades. An angle of 45
d^rees will be found satisfactory.

After turning the body or holder to size, and cutting the threads
to rec«ve the nuts, the slots for the blades may be milled. These
should be cut deeper at the cutting end, in order that any change in
the location of the blades may alter the ^ze of the tap. A taper of
■ff inch in 3 inches \a ample. If the slots are milled on the universal
milling machine, and the tap held in the universal centers, Fig. 115,
the spiral bead may be depressed sufficiently to give the de^ed angle.
Sometimes a pMr of centers mounted on speml ways is used and is

TOOL-MAKING 85

ntld in the milliDg-machine vise at the desired angle. The milling
cutter should be set about jy inch ahead of the center, in order that
the face of the blade may be milled enough to take any inequality
in the teettt.at the cutting face._ This b occas ioned by the thread

tool striking the face nlien it starts to cut. The amount milled
should be just enough to leave the cutting face radial. The blades
should be of an exact length and fit accurately in the slots. A gage
of the form shown in Fig. 1 16 will insure uniform length. After the
blades have been carefully fitted to the slots and to the gage, they
should be inserted in the holder and secured by the nuts, as shown in
Fig. 114. The outside diameter is then turned about .005 inch
smaller than the size the tap is to cut, and the threads very carefully

cuti after this the faces of the blades should be milled, as explained,
the cutting end chamfered, and the necessary amount of clearance
given the cutting edges by filing. The blades are now ready for
hardening.

Puring this process the blades should be subjected to a slow
heat in a muffle furnace or a tube. When the bkdes reach a low,

TOOL-MAKING

uniform red Jieat, they should be immersed in a bath of lukewarm
water or brine, and worked up and down to insure uniform results.
After hardening, they may be brightened and drawn to a deep
straw color.

For this operation it is well to place all the blades in a pan
having a long handle, as shown in Fig. 117. Coarse sand to a depth
of about 1) inches may be placed in the bottom of the pan with the
blades. The pan should be placed over a bright fire, and shaken
carefully, so that the teeth will not be dulled by striking the other
hardened blades. The motion causes the pan to heat uniformly,
and the sand keeps the surface of the work bright so that the temper
colors may be readily seen. This method of drawing temper will be

(^-

Fig. 117. Tempering Pan for Taps

found very satisfactory on many classes of work. It is also used
extensively where a great many pieces are to be colored uniformly
by heat.

Threads. Forms. Taps oneK^uarter of an inch in diameter and
smaller are, as a rule, made with V-threads whose sides form an

included angle of 60 degrees, or, with round top
and bottom threads. Taps larger than one-
quarter inch are made with the United States
Standard form of thread, which has an included
angle of thread of 60 degrees, the same as the
V-form, bat with one-eighth of the altitude
removed from the top and one-eighth filled in at the bottom, as
shown in Fig. 118. The V-shaped thread taps are made in various
pitches for each different size, but the United States Standard has a
definite pitch for each diameter.

Diameters. Below are given formulas for finding the diameters
at the bottoms of threads, or tap-size drills for the V-thread, and
the United States Standard thread. In both formulas, i$« desired
size; T == diameter of tap; N » number of threads per inch.

Fig. 118. Form of

U. 8. Standard

Thread

TOOL-MAKING

Formula for V-thread:'

Formula (or tlie L'nJted States Standard thread:

As an example of the working of the forrauJas, we will soli-e a
problem by each.

(a) The tap size drill for a I J-ineh diameter by 6-thread V-tap
may be derived by applying the formula for the V-thread, as folloiis:

= l.25-.2888 = .90l in.

(b) The tap size drill for a 1-inch diameter by 8-threud I'.S.S.
tap may be derived by applying the formula for the United States
Standard thread, as follows:

= l-.1625=.8375in.

Tap* for Square Tkrtoda, Although the square thread is not so
extensively used as formerly, having given place in many shops to
the Acme Standard, yet it, is some-
times necessary to make taps for
this form.

Steel sufficiently large should be
selected, the decarbonized portion
removed, and the shank turned to
size. The square should be milled

for R wrench and the size and num- j, ^^^ ^ Thi™iT«ii

ber of threads per inch stamped on

the shank. The cutting end of the tap is turned to size, the
necessary amount of taper given the tap, and then the threads
are cut.

The tool used for cutting square threads is similar in form to a
cuttmg-off (parting) tool, except for its angle side rake. It should
be made of the proper thickness at the point, but should be some-

8ft TOOL-MAKING

what narrower back of the cutting end. Fig. 119, in order that it may
clear when cutting.

The thickness of the cutting end should be one-half the distance
from the edge of one thread to the corresponding edge of the next
thread. For a square thread of i-inch pitch, the land and space
tc^ether would lie J inch, while the land and space would each be
J inch wide. The point of the tool should be ! inch thick.

The sides of the tool from A to B, Fig. 120, must be inclined to
the body as shown, the amount of the inclination depending upon the
pitch of the thread and the diameter of the tap to be
cut. This may be determined by the method shown
in Fig. 121. Draw the line AB and at right angles
to it draw CD, whose length must be equal to the cir-
cumference of the thread to be cut, measured at the
iKittom or root of the thread. On AB lay olT from
the point C a distance EC equal to the pitch of the
thread to be cut, and draw the line DE, The angle
f^. 120. CDE will represent the angle of the side of the
'^"tS""' ttiread; the angle of the side of the cutting tool must
be sufficiently greater to gi<e the necessary clearance.
It is advisable to cut the thread first with a tool somewhat nar-
rower than the required width, and to finish with a tool of the
proper thickness.

Square-thread taps may be fluted according to directions given

for V-thread taps. If a tap b intended to cut a full thread, ii must .

be well backed off, in order to

avoid the necesnity of using =*

much force that the tap would be

broken. When a tap is to be

used to size a hole whose thread

has been cut by a smaller tap,

very little clearance is necessary,

Lefl-lland Thread. Taps

are made with left-hand thread

for tools requiring such thread.

Many times fixture jaws are made

le to hold the work, and are opened

in pairs, that is, two jaws ai
and closed by turning a sci

IT which passes through a threaded por*

TOOL-MAKING 89

tion in each. One jaw has a right-hand thread tapped in it
while the other has a left-hand thread. The screw is made
with a righthand thread on one portion and a left-hand thread
on the other. If the pitch b the same on both threads the jaws
will open and close uniformly and will accurately center pieces of
various sizes.

It is necessary, of course, to back off the cutting lips of a left-
hand threaded tap on the opposite side of the end from that backed
off on one that is right-hand threaded.

Left-hand threaded taps are stamped with an L to prevent
confusion, for while it is possible to detect the difference in the way
the threading runs, in the case of coarse pitches, yet without a dis-
tinguishing mark the workman would often waste valuable time
trying to use a left-hand tap for a right-hand tap.

Steel for Taps. While ordinary crucible tool steel is ejctensively
used in making taps, many makers assert that the best steel for use

Fi«. 122. Typical Tap Wrench
Courtesy of S. W. Card Manufacturing Company, Mansfield, Maasachusats

in tapping cast iron and brass is one which has, in addition to the
usual composition of high-carbon crucible tool steel, from two to
three per cent tungsten. It is said that the amount of change in
length due to hardening is the same for tungsten steel as for most
tool steel.

Vanadium tool steel b used rather extensively in making taps
for tapping steel and is especially satisfactory in making long stay-
bolt taps. It is strong and is not so easily broken by shock and
irregular strains as ordinary tool steel, nor is it so easily affected by
slight variations of heat when hardening.

There are several oil-hardening steels on the market that
have won the approval of the tap-makers. The taps made from
some of these steels, it id asserted, will not change in pitch when
hardened.

Tap Wrenches. A solid tap wrench may be made for taps
whose squares are all of a size. This wrench b forged nearly to

90 TOOL-MAKING

shape, the liAiullcs turned to a'lze In the lathe, and the squtue hole
in the center drilled and filed. For general shop work adjustable
tap wrenches are commonly used, Fig. 122.

Tap Holders. \Yhen holes are to be tapped to a uniFonn depth
in a screw machine or a turret lathe, a tap holder b used which auti>
rratically releasea the tap when it reaches the required depth. A
vet;' common form, which gives excellent results whe» properly
made and adjusted, b shown in Fig. 123. Its essential parts are a
sleeve A , which fits the tool holes in the turret of the screw machine,
and B tap holder B, which fits the hole in the sleeve in such a manner
ss to slide longitudinally. The sleeve should be made of tool steel,
if of a diameter that makes the wall around the hole thin; tlie hole
should be drilled and reamed to size, and the outside turned to ^ze.
The portion oE the sleeve which enters the hole in the turret must
be a snug fit. The tap holder should be made of tool steel, or of a

grade of machine steel possessing great stiffness and good wearing
qualities. After roughing out to sizes somewhat larger than finbh,
the end which is to hold the tap may be turned to size, and the stem
end, which b to run in the sleeve, fitted, after which the hole /,
to receive the tap, may be made of a convenient size. In order that
the hole may be perfectly concentric with tlie holder, it will be neces-
sary to run the lar^e end of the holder in the steady rest of the lathe;
the opposite end should be fastened against the head center of the
lathe in such a manner that the stem runs perfectly true. With work
ot this nature, the head center of the lathe must be in good condition
and run true.

After the hole has been drilled somewhat smaller than finbh
size, it bnccessaiy to tniethe hole tvith a boring tool; the hole should

TOOL-MAKING 91

be bored to within .010 inch of finish size, after which it may be
reamed with a rose reamer. Before reaming, however, the outside
edge of the hole should be chamfered to the shape of the point or cut-
ting end of the reamer, to avoid any possibility of the reamer run-,
ning. Some tool-makers never ream a hole of this nature if it can be
avoided, always boring to size with a tool that makes a smooth cut.
If extreme care is used and the iioles are finished to size with a
reamer, results good enough for a tool of this character may be
obtained. .

TOOL-MAKING

PART n

STANDARD TOOLS

THREAD-CUTTING DIES

The size of a die is alwavs denoted by the diameter of screw it
wilt cut; a die that will cut a ^-inch screw is called a J-inch die,
irrespective of the outside diameter of the die itself.

Thread-cutting dies are made solid or adjustable. Solid dies are
suitable for work that does not require extreme accuracy. They are
comparatively Inexpensive, and can be
used to advantage as a roughing die
when an adjustable die is used fur 6n-
ishing. Owing to the tendency of dies
to change their sizes when hardened, and
to the fact that there is no provision for
wear, solid dies cannot be used where
work must be made to gage. They are
extensively employed in cutting threads
on bolts, and for this class of work
are made square, as shown in Fig. 124.

SOLID TYPE

Shaping Square Blank and Cutting Threads. In making a square
die, the blank may be machined to thickness and to size on the
square edges. One of the flat surfaces should be coated with blue
vitriol, or the blank may be heated until it shows a distinct brown
or blue color. The center may be found by scribing lines across
comers, as shown in Fig. 125. It should be prickpunched at i4,
where the lines intersect. The die blank may be clamped to the
faceplate of a lathe, and made to run true by means of the center
indicator. If there is no tap of the proper size, and only one die
is to be made, the thread may be cut with an inside threading tool,
provided the hole is of sufficient size; if not, a tap must be made.

Fig. 12^. t^quAfc Die

TOOL-MAKING

Fig. 12&.

Locating Cealer of
Die Bl»n

.1!

[f the thread ts cut with a threading tool, the size must be determined

by means of a male gage, which may be a screw of the proper size.

Chamfering. After threading, the
hole should be chamfered to a depth of
three or four threads, the amount depend-
ing on the pitch of the thread, a fine pitch'
not requiring so many threads chamfered
as a coarse pitch. The chamfering should
not be much larger on the face of the
die than the diameter of the screw to be
cut. Figs. 126 and 127 show two views
of a die chamfered and relieved on the
cutting edges. The chamfering should be
done with a countersink or taper reamer
of the proper angle. In the absence of
such a cutter, a tool held in the tool post
of the lathe may be used.

Number of Cutting Edges. Most
manufacturers making dies for the market
give four cutting edges to all sizes up to
and including 4 inches. When dies are
made in the shop where they are to be

used, custom varies. Some tool-makers advocate

three cutting edges for all dies smaller than {

inch, and five or more cutting edges for dies

above 2 inches. The objection to more cutting

edges than are absolutely needed on large dies is

the iiicrease in the cost of making.

When making dies for threading tubing, or

for work where part of the circumference is cut

away, it is better to give them a greater number

of cutting edgeathan would otherwise be the case.
Rake of Cutting Edges. For general shop

work, where the dies are to be used for all kinds

of stock, it is advisable to make the cutting

edges radial, as shown in Fig. 128, the cutting

edges AAAA all pointing to the center. For brass castings,

the cutting edges should have a slight negative rake, as ^hawn

FIc- 180. Chamfered Die

Fig. 127. Seetioa Shov
ing Chamfered Thread*

TOOL-MAKING

in Fig. 129, the cutting edges A AAA all pointing back ol the
center.

Clearance Holes. After threading and countersinking (cham-
fering), screw in a piece of steel threaded to fit the die. and face

Fig. 1J8. Dio with Radial Cutting
Edges

Fig. 129. Die with Threads Hav<
.ing Negative Rake

it off flush. Lay out the centers of the clearance holes on the back
of the die, and drill a hole the size of the pilot of a counterbore
whose body will cut the right size for the clearance hole. For dies
from I to J inch in size and having four cutting edges, the centers
of these holes may be the intersections of a circle, having a diameter
equal to the diameter of the screw to be cut, with lines drawn across
the corners, as shown in Fig. 130. Frickpunch these points. For a
die having four clearance holes* whose centers are laid out in thb

Fig. 130. Method of Laying Out
Die Blank

Fig. 131. Clearance- Holes in Die
Blank

way, it is customary to make the clearance holes one-half the size
of the die; that is, clearance holes in a J-inch die would be J inch.
The width of the top of the lands A, Fig. 131, should be about ^
of the circumference of the screw to be cut.

M TOOL-MAKING

The diameter pven Tor the clearance holes does not apply to
diesBBiBllerorlargerthan the sizes mentioned () to 1 inch),e^>eciBlly
if the dies are to be used in the screw machine, ta the clearance
holes not only provide a cutting edge, but also make a convenient
[dace for the chips; if the holes are so small that the oil cannot wash
the chips out, the chips dog the holes and tear the thread.

For Email dies, the clearance holes are of a size that allows the
chips to collect in the holes without tearing the threads, and they
are located at a greater distance from the center of the die, in order
to give sufficient strength to the lands. The desired shape and
thickness may be given the sides of the lands by filing. When it
is considered advisable that screw dies above ] inch have larger
clearance holes than the size mentioned, the holes should be located
at a distance from the center of the die that will give the desired
thickness to the land.

Circular Dies. For screw-machine and turret-lathe work, dies
are generally made circular^ and as holders for dies are part of the
equipment of every shop having screw machines, the dies should be
made to fit these holders; but it is not considered good practice
to make the diameter of dies less than 2} times the diameter of the
screw to be cut, and the thickness of the die 1} times the diameter
of the screw.

ADJUSTABLE TYPE

Method of Adjustment. While round dies for screw-aiachine
work may be made solid for roughing out a thread that is to be finished

by another die, the finish die should be made adiustahle. When mak-
ing adjustable dies, the general instructions given for solid dies
may be followed, except that some provision must be made For

TOOL-MAKING

kdjintment. This U done by split^n); the dies at one side as shown

at A, Fig. 133. In order th«t the die may not spring out or shape

in hardening, it is ■dviasbie to cut the

dot from the center of the die, leaving a

thin margin as shown at A, Fig. 133;

after the die is hardened, this may be

cut away with a beveled emery wheel.

If the thickness at B is too great to I

allow the die to close readily when

adjusted to size, the hole may be drilled

and connected with the clearance hole

by,r

isoFb

KCUt.

Die Holders. If many round dies
of the same diameter are to be mode, it is economical to have a
bolder with a shank which fits the hole in the spindle of the lathe;
the opposite end should be made to receive the die blanks, which
should be turned to fit the die holder in the screw machine. Fig. 134
shows the holder to be used in the lathe. A represents a die blank
jn the holder: B is the shank which fits in the spindle of the lathe;
C H a recess in the hoi ler to provide tor the projection left on the
blank when it is cut from the bar, and also to provide an opening
to receive the drill and tap after they run through the die. After
the blank is placed in the holder and secured in position by the

i^rew DIJ, the outer surface may be faced smooth and true with the
circumference, after whicK the blank should be reversed and thf
opposite side finished to the proper thickness. The die a now ready
to be drilled and tapped.

98 TOOL-MAKING

Drilling and Tapping. Before drilling, the die should be carefully
centered in the lathe. To insure a full thread in the die, a drill a few
thousandths of an inch smaller than tap size should be used, after
which a reahier of the proper size may be run through. When tapping
the thread, it is advisable to use two or three taps of different sizes;
the finish tap should be ^he size of the desired hole in the die, and
should be of the form known as screw die hob. Where several taps
are used for a die, there should be some difference in the diameter so
that any inequality in the shape or pitch of the thread may lie
removed by the larger tap; otherwise imperfect threads will result.
For instance, if three taps are to be used for a }-inch die, the first
one may be .230 inch in diameter; the second .240 inch in diameter,
and the finish tap, if the die is to be solid, .250 inch in diameter.
If it is to be an adjustable die, the finish tap should be .253 inch in
diameter, in order to furnish clearance to the lands when it is closed
to .250 inch.

Hardening and Tempering. Carbon Steel, Dies should be
heated very slowly for hardening, either in an oven furnace, or in
some receptacle that protects them from the action of the fire. When
heated to a uniform low red, they may be immersed in a bath of
lukewarm brine and worked back and forth to insure hardening the
threads. The temper should be drawn to a full straw color. If it
is an adjustable die, the portion marked B, Fig. 133, should be drawn
j|o a blue colof in order that It may spring without breaking. This is
done by placing this portion of the die on a red-hot iron plate; or the
jaws of a heavy pair of tongs may be heated red hot, and thedie grasped
in the tongs and held until the desired color appears. The blue color
must not be allowed to extend to the threads, or they will be too soft.
When the desired color has been obtained, the die may be dropped
into oil to prevent drawing the temper more than is desired.

High-Speed Steel. A great many threading dies are made from
high-speed steel. In order to secure the best results it is necessary to
harden them properly. Tools having projecting portions that must
retain their exact shape and size cannot be heated to so high a tem-
perature as lathe and planer tools that are to be ground to shape
after hardening.

Threading dies should never be hardened in a blast of air, as
the oxygen in the air might attack the metal, oxidize the threads,

TOOL-MAKINQ 09

ud M spml the die. A rumoce spedally deaiKned for such tooh
is shown in Fig. 22, Part I. The die may be suspended by means of
B hook, or a specially de»gned holder in the center of the furnux.
The flomecircuktingaroundtheoutsideof the opening in the furnace
bwves the center portion unaffected hy the blast. When the tool
has reached a temperature of 2150° F., it should be removed and
immediately plunged into a bath of cottonseed oil and worked
back and forth to force the oil through the opening. Threading
dies should have their temper drawn to 4W F. in order to reduce
the brittleness to a point where the cutting edges will stand up

Better results are achieved if the dies are pack hardened. Heat
them to a yellow heat and allow them to remain at this temperature

CDlUrlii'HpriniDIa

for from one-half hour to one hour; then quench them in cotton*
seed oil. When cold, the temper may be drawn to 480" F.

Spring Screw-Threadii^ Dies. This form of die, Fig. 135. ia
adjusted by means of a clamp coHar as shown in Fig. 136. In some
■hops it is the only form of screw-threading ijie used for scre<p-
machine work. When so used, it should be fitted to one of the
holders on hand, provided there is one of the proper si^.

Average dimensions of spring dies are given in Table V These
sixes are used by a manufacturing concern employing; a great many
■crew-threading dies of this description. It is, not necessary to follow
the proportions given, as they are intended only as a guide, and inay
be changed to suit circumstances.

For unifonn and well-finished threads, two dies should be used,
<ae (or toughing, and one for Gnishing,

TOOL-MAKING

TABLE V

"•■■r.r-

„.....„,

'■l-.T

Si'

l|£i'

Vihetv maii.v dies of a size Hre made, it is best to have a holder

with a shank titling the center hole of some tatbe. The stock can

be machined to ilze end cut to lenfcth. The clearance hole in the

back of the die ^l10uld be first drilled somewhat larger than the

diameter of the screw to be cut. For dies up to and including i inch,

thh excess in lixe should be ^ inch; for dies I to I inch, It should

be A inch; for dies i inch

and over, it should be from

A to I inch. After drilling

the clearance hole, the die

should be reversed in the

holder, and drilled and

tapped the same as a round

die, using a hob to finish the

[■'or general work, the
die should have four cutting
edges, making the lands
about one-«xteenth the cir-
cumference of the screw
' to be cut. Chamfer about

liiiiMiiu^ ' simpioe m'S?' three threads. The length

of the threaded portion of
the die should not exceed one and one-quarter times the diameter
of the screw to be cut. To [)ro:iuce the cutting edges, use a 4&-dc«ree
double-angle milling cutter. Fig. 137, which should be of suffi-
ciently larga diameter to produce a cut, as shown in fig. 138.

TOOHrfAKINa

101

The elumfered edgea should be relieved, and the cutting
edges finished with b £ne file. Stamp the size and number of
Chreads on the back end of the die, as shown in Pig. 138, and then
harden.

Hardeninf. The die should be heated in s tube and hardened
in ft jet of water coming up from the bottom of a tank, in order
that the water may enter the threaded portion. The die should be
hardened a little farther up than the length.gf the thread, and should
bemovedupanddownin the bath to prevent B water line; the temper
sfiould be drawn to a full
straw color.

Malla^U Iron Cot-
tan. Where many clamp
Dollars are usedi castings
of malleable iron or gun
metal may be made from
a pattern ; the hc^e should
be cored to within A inch
of finish size, drilled, and
reamed. When the screw
hole has been drilled and
tapped end the collar
split, it is ready to use.
If the surfaces are fin-
bhed, the cost is mate-
rially increased.

lUuatralton of Spring Die. The form of spring die shown
in Fig. 139 is especifllly adapted for heavy work; the jaws, being
heavy and well supported by the cap, do not spring when taking
heavy cuts. One end of the cap has an internal thread which
screws on lo the end of the shank, thus drawing the cutting
end o( the too! securely against the shank. This also provides
a means o( adjusting the size of the cutting end, as the cap is
tapered on the inside at the outer end lo fit the taper on the outside
of the jaws- A locking nut fastens the cap securely when it has
Iteen set to the right size. The cutting end of the die has groove^,
as shown at n. These grooves engage with tongues on the shank to
prevent tuminj;.

102 TOOL-MAKINQ

Die Holden. When cutting threads in scRw machines and
turret lathes, dies are held in die holders, which ore constructed in
two parts, as shown in Fig. 140. The shank A fits the hole in the
turret, while the die holder B has a stem that fits the hole in the
shank. While the die is cutting, the pins D and C are engaged, and
prevent the hoMer B from turning. When the turret slide of the
screw machine has traveled to its limit, the holder is drawn out of
the shank until the machine is reversed, when the pins engage on
their opposite sides. A pin is put through the stem of the holder at
E; this strikes the end of the shank just at the time the pins D and
f! become disengaged.

Shank. Both shank and body may be made of machinery' steel;
the shank may be finished to size, except the portion marked A,

which should be left .010 inch large for grinding. The front end d
the hole should be rounded, as ^own, to allow the fillet in the shoulder
of the stem to enter. This fillet is left for strength. The pinhole
shouM be drilled and reamed. When the holders are to take dies
not over | inch in size, this pinhole may be A inch in diameter;
for dies from i to ft in size, the hole should be \ inch in diameter.
As the dies increase in size, the pin mu9t increase proportionately.
The shank may be casehardened in a mixture of granulated charred
leather and charcoal; it should run about two hours, and then be
dipped in a bath of oil. The hole should be lapped straight and true,
and the outside ground to fit the hole in the turret. The pin C
should be of tool steel, hardened and drawq to a blue color, aod
forced inia place.

TOOl^-MAKING 103

•Holder, The holder B may be made from a forging, or turned
from a solid piece. After roughing to size somewhat larger than
finish, the stem may be turned and fitted to the hole in the shank,
in which it should turn freely. The larger portion, or body, is next
turned to size. This should be run in the steady* rest, and the end
drilled and bored for the die and for ctearaijice back of the die, as
shown. Three or four large holes drilled into the clearance hole
provide the chips and oil with a way of escape, thus preventing
injury to the threads of a screw long enough to reach through the
die when being threaded.

Screw Holes. Screw holes should be drilled and tapped as shown.
The screws are to hold the die in position in the holder, and also
to adjust to size dies that are split. The stem may be placed in
the shank, and the pinhole transferred through the pinhole in the
shank into the body; this should be done before the pin C is pressed
into place. The pin D should be hardened the same as C. The pin-
hole for the pin E should be drilled in a location that allows C and
D to become disengaged, and yet have no play between them.

COUNTERBORES

Two-Edged Flat Counterbores. Counterbores are tools used for
enlarging a hole without changing its relative position. For an
emergency job and for a small number of holes, it is advisable to make

BOHf

-■I

Fill. Itl Flat Couni«>rbure

as cheap a form as is consistent with the work to be done. Probably
the cheapest counterhore that will do satisfactory work is the one
shown in Fig. 141. This can be forged so as to requijre but little
machine work. After forging, it is turned to size, and the shank A
and .pilot B finished with a fine file before being taken from the lathe.
The cutting edges CC should be faced true and smooth. The neck-
ing between the pilot and the body should be cut with a tool having
the comers slightly rounded, . to decrease the liability to cracking
when the counterbore is hardened. The flat sides D of the body

104

TOOL-MAKING

may be finish-filed; the edges should be drawfiled, and more stock
removed on the back than on the cutting edge, to prevent binding.
File the cutting edges for clearance, as shown at E. The pilot and
the body should be hard the entire length i or they will wear and rough
up so that they cannot cut a smooth hole. Draw the temper to a
full straw color. Unless intended for accurate work, the tool need
not be ground.

' Counterbofes with Four Cutting Edges. For permanent equip-
ment, counterbores are usually made* with four cutting edges, as
shown in Fig. 142 and Fig. 143; Fig. 142 represents a taper-shank
counterbore for a taper collet, while Fig. 143 has a straight jihank to

PiK. 142. TyplcHf Coiinierborr with TapiT Mhaiik

Fiff. 143. Typical Counterburf with 8tr«iffh( Hhtink

be used in a chuck or collet having ^ straight hole the sixe of the
shank.

Counterbores for screw holes are usually made in sets of three
— one for the head of the screw with pilot, or guide, of body size;
one for the head with pilot of tap-drill size; and one to enlarge a
tap-drill hole to body size.

Directions for Making. The following instructions apply to
counterbores with either straight or taper shanks.

Tvnivng io Size. Take stock somewhat larger than the finish
size of the counterbore. Turn a roughing chip all over the piece;
turn the necked portion between the shank and body to size, and
stamp the size of counterbore and pilot as shown in Fig. 143; turn
shank C, body ..-I, and pilot B .015 to .020 inch above finish sizes
to allow for grinding. In the case of the taper-shauK counterbore
the tenon should be milled.

Milling Grooves. The counterbore is now ready to have the
grooves milled to form the cutting edges. One method is to cut

TOOL-MAKING

105

them with a right-hand spiral of from 10 degrees to 15 degrees; the
other method is to cut the grooves straight. The former has the
effect of nmning chips back from the cutting edges, and works very
well on Mrrought iron and steel ; while the latter method b considered
more satbfactory for brass and cast iron, though it too works well

Fi«. 144. Sketob flhowinc Cleiiranoe of Cutiinn
EfUtf* of CoiintArhoiti

FiM. 14A. Sketch ShdwtnK
Clearance of Land;*

on wrought iron and steel. The cutting edges are given clearance
by filing, as shown at .1 in Fig. 144. If the counterbore is to be
used for brass, it is necessary to give clearance to the lands also,
as shown at AAA A, Fig. 145.

Centering. When centering counterbores, or any tools whose
centers are not to be used after the tool is finished, the drill should
be small, and the countersinking no larger than is necessary for
good results in machining. If large centers should, by accident, be
put in the ends, the one on the end to be hardened should be filled
with fire clay moistened with water to the consistency of dough,
or with graphite mixed with oili this prevents steam from forming
in the hole and .cracking the tool when dipped in the bath. If the

Kl«. 110. Sleeve for CounterborM with Hole* f^iircer than Pilo^

piece is to be heated in lead, the filling should be dried thoroughly
before immersing.

Use of Sleeve, Solid counterlx)re3 can be used with holes larger
than the pilot by forcing a sleev.e over it, as shown in Fig. 146. B and
C are two views of the sleeve which is to be forced on to the pilot A^

S TOOL-MAKING

Grinding. After hardening, the couiitertMre may be groimd
size oil the shank, body, and pilut; the tihauk should be ground
9t, as the length U greater, and, in the case of a counterbore having

a straight shank, the grinder may be adjusted to perfect aligmnent
by measurement.

Two-lipped counterborea are sharpened by grinding on the flat
faces marked D, Fig, 141; & four-tipped counterbore is ground
on the flat ^de of the groove, as D, Fig. 146.

Counlcrbores for Special Catei. It is necessary many times
10 produce a hole oF a given taper extending into a piece of work, as
shown in Fig. 147, where the hole must be exactly in line with a
drilled hole already in the piece. This can be done by using a counter-
bore of the deaign shown in Fig. 14S. At other times, it b necessary
to produce an impression of special form which must be true with a
drilled hole. In such cases a counterbore may be made whose pilot
is the size of the drilled hole, and whose body has the tonn of the
desired impression, Fig. 149. As the cutting edges of this counter-
bore cannot be ground after hardening, they must first be backed
off for clearance with files and scrapers, and special pains taken
during the hardening to pre-
it springing. This can be
' done by heating the piece in
muffle furnace and turning
it frequently to prevent un-
even heating; or by placing
the tool in a [Hece of gas
{Npe in an ordinary fire, quenching it in lukewarm water, and draw-
ing the temper to a full straw cobr, 460° P. Better results follow if
the tool b pack hardened, and then quenched in raw linseed oil
or cottonseed oil.

TOOLrMAKING

107

Facing Tool with Inserted Cutter. Where a limited number
of holes are to be counterbored; the tool shown in Fig. 150 may be
made. All that is necessary in making this tool is
a piece of stock, A^ the size of the hole to be coun-
terbored, and a piece of drill rod for the cutter B;
the latter is filed to a cutting edge, hardened, and
driven into place.

If accuracy is essential, the piece of drill rod
must be cut off somewhat lunger than the diameter
of the required hole; it should be driven into the
hole in the bar leaving an equal length on each

side, then turned to the cor-

i I !:| ^^^^uT/P^PW '■^^ diameter and filed to

shape. If several cutters are
to be used in the same bar,
or if the tool is to be used as
a facing bar to square a shoulder inside a piece
of work, Fig. 151, the cutter B is removed from
the bar; after the bar is in place, it is inserted and
held by a set screw C.

Counterbores for Large Work. For large work.
Fig. 149. a counterbore may be made, as shown in Fig. 152,

for'Makinc A bciug the cuttcr bar which should be made of

Hole tool steel iV to i inch larger than finish size.

Fig 150 Facing Tool wiih Inserted Cutter

Cvtting Slot. After taking a roughing chip, leaving the bar
a trifle large, a slot should be made to receive the cutter C. This

108 TOOHtfAKINO

b done by drilling a aeries of holes as shown in Fig. 153- After prick-

punching the-bar, it should-be clamped to a drill-press table, and

held in » pair of V-blocks. To insure the drill holes going through

the center of the bar the

prickpunched marks should

be set as f olkiws : Place the

blade of a try square agu'nst

one side of the bar; measure

to the center; then place the

square against the opposite

side, and measure in the

. same manner. When the

distance from the square

blade to the centers is the samaon each aide, the piece is in the proper

portion for drilling The drill-press table may then be swung around

until the prickpunched marks are in proper k>cation with the spindle

of the press. After drilling, a drift may be driven through to break
the walls separating the holes, and the slot filed to size.

FithlaU Cvtter. Where the necessary tools are, to be obtained,
there is a much more accurate and satisfactory method of producing
_ the slot. It consists in

J cutting the slot from the
/ solid with a fishtail out-
m ter. Fig. 154. The piece
' of work is held on the

' '"* centers of the dividing

.head: the cutter is fed into the stock, and the table moved to
produce a slot of the right length, the operation being repeated
until the slot is quite through the [nece.

000

TOOI^MAKING 109

When using this form of cutter take light cuts and fine feeds,
and run the cutter at high speed, keeping it flooded with oil. Before
starting, make sure that the cutter is well sharpened and that it
ha^ plenty of clearance at the edges to prevent deviation from a
straight line. If conditions are right, this cutter will produce a
straight, true slot in a fraction of the time necessary to drill and file
it out. If it is essential to have the ends of the slot square, they
must be filed or broached to shape after cutting.

This type of cutter is used very extensively in shops for building
machines the spindles of which must be provided with slots to receive
a center key used in driving shanked tools out of the spindles.

Finishing Tool. The bar, Fig. 152, should be placed with one
end in the steady rest, and the other end strapped to the head
center of the lathe. The screw hole in the end is now drilled and
tapped into the slot, ii^order that the screw may bind the cutter. The

FiK. lot. »>p(>riNl Finbtitil Cutt-er

end should be countersunk to provide a center for finish turnkig.
The bar may be turned to size at yl, and the pilot finished to size.
The screw cap D should have a head ^ inch larger than the part B, in
order that it may hold the sleeve in place should the latter have a
tendency to come off when removing the counterbore from the hole.
The cutter C should be a close fit in the slot. A headless screw should
be made short, so that it will not interfere with the dead center of
the lathe when it is screwed to place against the cutter blank. It is
intended to be used when turning the cutter to the right diameter
and should be kept for that purpose.

Counterbores with Inserted Pilots. These are useful when the
counterbores need frequent sharpening, or when holes of a variety
of sizes are to be counterbored to the same size. A common form
of counterbore having an inserted pilot is shown in Fig. 155.

DrilHrig and Tvrning to Size. When making this counterbore,
the stock should have a roughing chip taken off, and the hole E

110 TOOL-MAKING

drilled part way from the shank end. This lirilling may be done tn
the speed lathe, the (trill being held in a chuck in the head spindle,
tlie center in the opposite end of the piece should be on the dead

cwiter of the lathe. If the piece is turned a one-half revolution
occsajoiially, the drill will cut accurately enough, as perfect align-
tnent is not necessary in this hole, since it is intended only for use
when driving out the pilot.

After drilling, the shank end shouki be carefully coui)tersunk
The piece is now ready to be turned to grinding size, which should
be from .015 to .030 inch
oversize. After the outside
has been turned, (he hole for
the pilot is drilled and bored.
the large end of the counter-
bore running in the steady

Culiing Edges. The coun-
terbore should have four cut-
ting edges for all ordinary
work; these may be made with
a side milling cutter the face
of which is sufficiently wide
to cover the width of tooth.
The form of cutter is shown

,».». i».i.,»n,™c..„„o».„»« '•" Fig- "»■ •■l>"« ■- •"■<
Cwiinr ■' "J'S 'i'"jf' "V'''" C"!""'- view of the teeth of the coun-
terbore is shown in Fig. 157.
When milling the teeth, the counterbore can best be held in the
chuck on the spiral head. If a more stubbed Form of tooth is needed
than the one shown in Fig. 155, the spiral head may be tipped to

TOOL-MAKING

111

Fig 157. End View of
Teeth of Couoterbore

the desired angle and the cutter fed through the counterbore, instead
of sunk into it.

Hardening. After milling, the j>urrs should be removed, and the
counterbore stamped and hardened. To harden, it should be heated
to a red nearly the whole length of body; when
dipped in the bath, it should be inverted in order
that the teeth may be uppermost; it should be
M'orked up and down rapidly in the bath until
the red has entirely disappeared, and allowed to
remain until cold. If the counterbore is larger
than 1 inch in diameter, the strain must be
removed immediately after removing from the
bath by heating the piece oVer the fire, . as already explained.

The pilot should be turned, as shown in Fig. 158. A and BB
should be left about .010 inch large for grinding after hardening;
C should be turned ^ itich smaller than the hole in the mill, as this
does not bear when the pilot is in place A slight depression should
be made between the head and the first bearing point B for the
emery wheel to pass over
in grinding A is the
only part that needs to
be hard, but, unless a
piece of tube is slipped
over the stem B when
the pilot is put in the bath, it will be almost impossible to harden
A the entire length and leave B soft. As A is likely to rough up
when used, it is best to harden a short distance on the stem B, unless
there should be a great dilTcrence in size between A and B. In the

Fig 158. Pilot for Counlerbore

Fib 159 Cover for Pilot When Hardening

latter case a tube, or a piece of iron with a hole drilled in the end
the size of B and having the end beveled, as shown in Fig 159, should
be slipped over B when the pilot is heated. The cover should be
sltpi>ed over the stern and up against the shoulder of the head to

lia TOOL-MAKING

prevent a water line, ir this precaution is taken, there is ito danger of

the pilot cracking under the head,

GnTBtiTig, After hardening and tempering, the pilot is grouDd

to size at A, and the portions BB are ground to fit the hole af
the cDunterbore. After grinding,
the pilot is forced into place The
counterbore may be ground with
the pilot in position. When the
counterirore U dull the pilot
should be forced out of it, and
the cutting edges ground with an
emery wheel.

Counterborei with Single
Edged Adjustable Cutter. A
very satisfactory form of adjust-
able counterbore that works well
where a tool with but one cut-
ting edge is needed, is shown in
Fig. 160. This tool has a rather
wide range of adjustment, and
can be made at a nominal cost.
The cutter A may be made
from carbon tool steel or high-
speed steel, according to the
use to which it is lo be put , it is
placed at an angle of 45' degrees
with the shank axis. The cut-
ter is adjustable to position and
locked by the knurled nuts DD
and bound by (he set screw C.
»«««xx The pilot E may be used in holes

'" "" S;^™ Adiiauw. of various sizes by providing
sleeves the holes of which fit the

pitet and the diameters of which fit the holes to receive them, Th«

shank B may be straight or tapering according to (he custom in the

individual shop.

This form of counterbore is sometimes provided with a rec>

tangiilar-shaped cutter instead of the round one shown. When this

TOOI^MAKING

•113

is desirable, the rectangular-shaped hole to recjsive it may be produced
with a fishtail cutter, described on page 108. In the case of the
oounterbore under consideration, however, it would be necessary
to turn the swivel table of the milling machine to give the desired
angle.

The fishtail cutter will produce a hole with rounded ends. If this
is objectionable, the ends may be filed square or may be squared with
a broach. For the general run of work, however, the rounded ends
are not objectionable. In fact, for the majority of jobs a round
cutter in a round hole, as shown in the cut, would answer as well as
one made rectangular in form, and could be made for a fraction
of the cost.

Combination Counterbores. These are used when it is necessary
to change the size of counterbore and pilot frequently. A shank

or bar is made to accom-

modate different sizes of

cutters, and sleeves serve

as pilots. In Fig. 161,

A is the cutter, and B

the pilot which is tapped

in the end to receive a

screw to hold the sleeves, and C is the shank which is held in a

chuck or collet when the counterbore is in use.

After taking a roughing chip off the bar, the end B is run in the
steady rest and the hole for the screw F is drilled and tapped. The
outside end is countersunk to a 60-degree angle to run on a center.
When machining the holder, the portions B, C, and D should be left
about .010 inch larger than finish size, to allow for grinding: if more
convenient, however, they may be left a few thousandths of an inch
above size, and filed to finish dimensions.

The body, or cutter. A, should have a hole ^ inch smaller than
finish size drilled through it; the outside surface should be turned off,
and the piece annealed. If a grinder having an internal grinding
attachment is at hand, the hole in the cutter should be left .005 inch
small for grinding. If the worker«does not have the tool, the hole
may be reamed to finish size. The outside diameter should be left
about .010 inch large; the ends should be faced to length, and the teeth
cut. If four teeth are to be cut, the work may be done with the

Fit- 161. Combination Counterbore

114

TOOL-MAKING

side milling cutter, shown in Fig. 156. The counterbore should be
held in a chuck on the spiral head spindle, which should be tipped
to produce a strong tooth, as shown in Fig. 161. Before hardening,
the hole should be drilled, and tapped for the screw H, which holds
the counterbore to the bar.

To harden, the counterbore should be given an even, low, red
heat, and plunged into water or brine in such a manner that the
bath will come in contact with the teeth. If the teeth are stubbed
and strong, the temper need not be drawn more than to a light
straw color.

The screw H should be made of tool steel and have a projection
J inch long on one end^ turned. to the bottom of the thread. This is
to enter a hole drilled in the bar or holder and keep the counterbore
from turning. The end of the screw should be about .005 inch smaller
than the hole. The screw should be hardened and drawn to a blue
color. The sleeve intended to go on the pilot E should be made of
tool steel, hardened, and ground to size inside and out. The screw
F may be made of machine steel, casehardened to the proper depth,
by heating it to a red and sprinkling with powdered cyanide of
potassium, then reheating and plunging it into water.

HOLLOW MILLS

Hollow mills are used in screw machines and turret lathes for
roughing down and finishing. They are also used in drill-press work

for finishing a projection
which must be in some given
position; in the latter case,
they are generally guided by
a bushing in a fixture, to
bring the projection into the
proper location.

PlaiirHoUow Mills. For
roughing out work on a screw machine or turret lathe, solid mills
having strong stubbed teeth are preferred because of their rigidity.
For finishing, they are made adjustable in order to get exact sizes.
Fig. 162 shows a plain hollow mill having the cutting end hollowed
out in the form of a V, in order that it may center itself when start-
ing to cut. Fig. 163 shows a form of plain hollow mill intended for

Fig. 162. Hollow MUl with V-End

TOOI^MAKING

115

use in squaring up a shoulder at the end of a cut that has been made
with a. mill of the form shown in Fig. 162. or it may be used for
roughing out a piece, but it will not center itself so readily as the

Fig 163. Hollow Mill (or Squuiag Up Shoulder

former one. For small hollow mills, some tool-makers advise three
catting teeth, while ot ers conte d t at better results re secured
with four teeth on all sizes.

Fig. 164. Hollow Mill with T*pered Hole

Bormg and Reaming. The rear end of the mill is bored some-
what larger than the cutting end, to allow it to clear on long cuts.
The cutting end must be relieved, or it will bind and rough the work
and probably twist it off in
the mill. There are sev-
eral methods of relieving j
mills; the most common
one is to ream the hole
tapering, making it larger
at the back end, as shown
in Fig. 164. Another Fig i65 Hoiiow miii wuh EdgN Fiiad

method is to file back of the edges, as shown in Fig. 165.

Uw of Mill Holder, For making several hollow mills having the

same outside diameter, it is advisable to use a holder of the form

116

TOOL-MAKING

shown in Fig. 166, which has a taper shank that fits the spindle of
a lathe. The hole in the other end of the holder should be the- size
of the holder in the screw machine or turret lathe, which holds the
mills when in use. The steel for the hollow mills should be cut to

Fig. 104. Holder for Hollow Mills

Fig. 167 Mill with • Stmng Tooth

length, and turned to the proper diameterto fit the holder. After
putting the blank in the holder, the ends may be squared, and the
holes drilled and, bored to the desired sizes. If the mill is to be one
of the forms shown in Figs. 162, 163, and 164, the cutting end may

be reamed with a taper reamer to

give the necessary clearance. The

reamer should be run in from the back

end in order that thb end may

be larger. For the form shown in

Fig. 164, the hole at the cutting end

should be straight and of finish size.

Cutting Teeth. The mill is now ready for cutting the teeth.

If four cutting edges are to be given, a side milling cutter may be

used, of a diameter about double the diameter of the hollow mill to

be cut. The blank should be held in a chuck on the end of the spindle

in the spiral head . For a st rong tooth,
the spiral head should be set at an
angle that will produce the tooth
shown in Fig. 167, by feeding the
milling cutter through the blank. If a
deei>er tooth is desired, the spiral head
must be set so that the blank will be
in a vertical position, and the milling cutter fed in until the desired
form and depth of tooth are obtained.

Adjustable Hollow Mills. These may be made by following the
instructions given for plain hollow mills, except that the mill must
be split, Fig. 168, to allow for alteration in size.

Fig. laS. Adjustable Mill

TOOL-MAKINQ

117

Metkoii ef AdjtutiMnt. There are two methods of »d}iut)og
the mill. In one the outside of the cutting end of the mill is tapend,
and a coUai having a corresponding taper hole is forced im the mill.
The collar closes it, and causes it to make a smaller cut The other
method ia to turq the outside of the hol-
low mill straight, and dote by means of
a clamp coDar, Fig. 169.

Cvttinf Teeth. As adjustable hollow
mills are generally used for finbhing cuts,
and not when taking heavy cuts, the ■
teeth may be made finer ^lan those of
solid mills used for roughing. The leeth, being neam together,
will finish a cylindrical piece more accurately than if the teeth were
cut farther apart. It is customary to give adjustable hollow mills
which are to be used for finishing, friHn six to eight teeth. The
cutting edges should be radial for most work. Better results wilt be
obtained if the hole in the cutting end of the mill is left .0&5 inch
small, and ground to »ze after the mill is hardened.

Hardening and Orlnding Hollow Mills. The hollow mill,
whether it be solid or adjustable, should be hardened u triSe farther

Vp than the length of the teeth, and drawn to a straw color. The mill
is sharpened by grinding on the ends of the teeth.

Hollow MUls with Inserted Blades. For large work, hollowmills
are made with bserted blades. The type shown in Fig. 170 does good
service mi iwugh work. The blades of this mill may be made of self-

118 TOOI^MAKING

hardening steel and inserted in a machbe-sMel body; the groove*
in the body, to recrive the bUdra. should be milled with a cutter
whose thickness corresponds to tbe size of the steel to be used for
jtbe blades. The grooves ore clit somewhat deeper at tbe front end
of the bolder, n order that the blades may have clearance to prevent
bintUng. The edge of the slot corresponding to the cutting edge
of tbe blade should be radial.

Two collars should be maile of machine steel, with holes suffi.

ciently large to allow their being placed on the mill when the

blades are in the slots. Each .collar should be provided with the

same number of set screws as there arc blades in the mill. One collar

holds the bhides in the holder, while the other is placed nearly at the

ends of the blsd* to support them while cutting. This form of mill

is used on cuts not exctcding oDe inch in length, as the blades must

project beyond the htJder to

the length of the euL

■. The size of cut may be

3p changed somewhat by setting

the cutters back or ahead in

the slots, or paper may be

" - I "I placed in the slots under the

blades to increase the diametn of the cut. I'he blades are set to

M even leng^ by bringing them against a surface perpendicular

to the axis of the body of the tool.

Hollow Mills with Pilot. It is often desirable 10 mill the outside
of* projection central with a hole passing through it. This may be
^one very satisfactorily with a hollow mill having a pilot, as shown In
Fig. 171. It is advisable to hold the pilot in place by means of a
set screw. In order to give clearance tb the teeth to prevent the
mill binding when cutting, the hole may be bored tapering, .010 inch
ih ) inch of length, maldng it largest at the back end.

When hardening a mill of this description, it is advisable to dip
it into the bath with the cutting end uppermost, working it up and
down rapidly. Aftef being hardened, it should be drawn to a straw
color. The pilot should be turned .010 inch above finish size, hard-
ened, drawn to a brown color, and ground to the desired dimensions.

At times it is necessary, or desirable, to use a hollow mill as a
Gounterbore; that is, it is necessary to enlai^ a hde all the way

TOOL-MAKING 116

through a piece of stock. As the core removed would bind and
stick in the hole b the mill, the hole is made eccentric. Fig. 172.
The pilot b concentnc with the outaide, and should uot be a tight

fit in the hole to be enlarged. The core removed will be smaller
tbftD the hole in the mill, and consequently will not bind.

FORMING TOOLS
Forming tools are used when several pieces are to be made of
exactly the SAme shape. They are particularly valuable for giving
the desired shape to fonned mills and similar tools, and in duplicat-
ing a given shape on
work produced io the y

Forming tools are ?

made flat and circular "N^

in shape. When used in
the lathe for shaping
such tools as milling ma-
chine cutters, they are
generally made flat; for
backing ofT formed mill-
ing machine cutters, they

are always made flat; for p, ^^^ ^.^^^ ^^^^^ ^^^

screw machines in dupli-
cating a pven shape, they are made both flat and circular.

Flat FoTmin^ Tools. The flat forming tool is made as a solid
cutler, the tool and shank being in one piece, Fig. 173, or the culler
and shank may be made separate, Fig. 174. When but one forming

120

TOOI^MAKING

[

tool is to be made, the former will be found to be inexpensive; but
for making many tools, it will be much cheaper to adopt the latter.
Holders, On certain classes of work, it is advisable to use a form-
ing tool on a holder of the kind shown in Fig. 175, which is known as

I — j I ■ a spring holder. On ac-

^ j >— N. / count of its design, it

may spring somewhat
when used on heavy cuts,
thus reducing the ten-
dency to chatter. It b
necessary to make these
holders of tool steel, giv-
ing them a spring temper
at the point marked A.
The slot B allows the
forming blade D to spring
away from the work
when under heavy strain. The blades may be planed up in long
strips and cut off the required length. The tongue E should fit the
slot C, which, with two cap screws through F and 0, securely holds
the blade in position.

Clearance, In order that a forming tool may cut readily, it is
necessary to give the surface marked B, Fig. 174, a sufficient amount
of clearance. For tools to be used for shaping milling machine cutters
and similar tools, a clearai^ of from 10 degrees to 15 degrees will

Fig. 171. Forminc Tool with Separate Shank

Fig. 175. Sprinc Forming Tool Holder

be ample; that is, the angle should be from 80 degrees to 75 degrees.
But if the tool is to be used for backing off the teeth of formed
milling machine cutters,- it is necessary to give a clearance of from
18 degrees to 22 degrees. When making a forming tool having the

TOOI^MAKINO

121

lequired angle at B, the shape can be produced by tipping the blsnk

to the correct angle and planing or milling with a tool having exactly

the desired shape. The tool used may be made of a ^ape enoogh

diSerent from that desired as to

produce the proper shape when

the cutter is in a vertical position,

and the blank at a given ai^le

from that position, as shown in

Fig. 176. Or the tool may be

held in the tool post (or in a

fixture made for the purpose) of

the shaper or planer at the same

angle as the blank being cut,

Fig. 177, and it will produce a

shape corresponding very closely

Screw-M^hfne Forming Tools. In screw-machine and similar
work for duplicating given shapes, a fonning tool is made like the
one shown in Fig. 178. A represents a holder used by the Brown and
Sharpe Manufacturing Company for use on their screw machines;

B shows the forming tool blank; and the desired shape is cut in the
surface marked C,

Circular Forming Tools. These are used very extensively
on screw-machine and sinjilar work. They are valuable on account

122

TOOL-MAKING

of the ease with which any number of them can be produced, pro-
vided a forming tool is used in producing the shape on the face, as
shown in Fig. 179.

Milling Cvtiing EdgesT^ After the blank has been given the proper
, ^^ shape, it may be milled asshown

Fie. 179.

SirailT^t FrtrminE Tool for Produc-
ing Circular Tool

in Fig. 180, in order to provide a
cutting edge. If it is desired to
produce a shape on the piece
being machined, to correspond
with the shape of a tool, it is
necessary to have the cutting
edge nadial. Fig. 180. In order
to feed the tool into the stock
faster than can be done with
the form shown, it is given
more clearance. Fig. 181. On a
tool whose cutting edge is not
radial and will not produce a
shape corresponding to its own,
it is necessary when cutting the
edge with the rake shown in
Fig. 181, to make the face of the tool slightly different in form from

that desired.

Preventing Cracks. After the cutting edge has been milled,

the name or number of the tool should be stamped on it, and it is

then ready for har-
dening. When ex-
tremely high carbon
steel is used, the tools
sometimes crack while
hardennig from the
strain incident to their
shape. Some tool-
makers overcome this

tendency by making two extra cuts in the edge, Fig. 183k

Lessening Need for Grinding. Two cutting edges. Fig. 183, are

often given a tool, in order that it may not need to be ground so

often as when it has but one cutting edge. It is not necessary to stop

Fig. 180. Culler with Radial
Culling Edge

Fig. 181 Cutter with Ofl-
wt Cutting Edge

TOOL-MAKING 123

the sere* machioe nearly so long to grind both cutting edges, aa to
9top the machine twice to griad the same edge, on account of the
time necessary to rig up the grinder.

Hardening, To harden, the too! should be heated to a low red,
and plunged into a bath ^^__..^^

of water or brine from [^ ^v <^ ^\

which the chai has \ \

been removed; it should i / \ ^^ /^^ 1

be worked aromid well f \ / I \ \,^ J |~~^

in the bath. If the V J \

temper is not to be \ V/ \. J

drawn after hardening, ^"^ ^ ^*- -^^

the tool may be held "^IS pm^oi '^"SlSikp." ^EEutSciuulSKlllB
over the fire after re-
moval from the bath, and heated sufficiently to remove the tendency
to crack from internal straina.

Tempering. On account of some weak projection, which,
because of its shape, is likely to break when used, it is sometimes
necenary to draw the temper. It is not always necessary to draw
the temper to a straw color, and as a light straw is the first temper
color visible, some other means must be employed. The tool may be
placed in a kettle of oil, and with the aid of a thermometer the desired
degree of heat may be accurately obtained. The writer recalls a

certain forming tool which was too brittle when left as it came from
the hardening hath, yet was not hard enough when drawn to even the
faintest straw color. After removing from the hardening bath, it
was placed in a kettle of boiling water and left about five miuutes.

124 TOOL-MAKING

The heat of the water at 212 degrees reduced the brittleness so that

the tool stood uo in good shape, yet was not perceptibly softeDed,

The following is an excellent plan: A bath of water havin

aboutoneinchofoUon top is made ready; the tool, after being heated

I hot, is plunged down through

; oil into the water. Enough

oil adheres to prevent the sud-

I den shock which the steel would

eive if plunged directly into

1 water. Pack hardening also

gives excellent results.

Tool HoMers. The form of
Fi«.i8i. c»..iHT»i(«H».i-c-« theholderforthetooldependson
the class of work to be done and the machine in which it is to be used .
Fig. 184 shows a design commonly used for hand screw-machine
work. If the cuts are comparatively light, the side of the tool and
holder may be flat, as shown. It, however, heavy cuts are taken
which would have a tendency! to turn the tool, the latter is often
made with a taper projection on one side. Fig. 185, the holder having

nt IM. Hokhr lor Auuulic «tr» Ri 187. Hobta. [or B»vj

MtcAiu Au an AuiQiniKD Michinc

B cOTreaponding taper hole to receive the projection. This projection
should be a good fit in the taper hole, but should not go in far enough
to strike the bottom; neither should the side of the tool bear against
the side of the holder.

TOOL-MAKING

125

Fig 1S8- Add|>tiDS Bolt

When used in automatic screw machines, the holder is generally
of a different shape from that used for hand screw machines. A very
common form is illustrated in Fig. 186. This holder is made in the
form of an angle iron, and is fastened to the tool rest by means of
the bolt shown. The tool b
secured to the upright side of
the holder by the bolt, witk
its head let into the forming
tool.

When extra heavy cuts
are to be taken with a form-
ing tool, it is sometimes considered advisable to make a holder of the
form shown in Fig. 1 87 The holder is bolted to the tool rest in the same
manner as the one represented in Fig. 186. A square thread having a
pitch of five or six threads to the inch is cut in the forming tool. The
thread should be a right- or left-hand one, depending on which side
of the machine the tool is to be located, the thread being such that the
tool will tighten by the pres-
sure exerted by the cut. To
get an adjustment, the thread
in the holder must be of ^
finer pitch than that in the
forming tool, and of the same
hand. This tool can, if de-
sired, be employed in the
ordinary' form of holder shown
in Fig. 186, by the use of the
bolt shown in Fig. 188.

At times, it is necessary
to use two forming tools;
these may be arranged to
meet the requirements of the
individual job. In Fig. 189
are shown two forming tools arranged to cut a desired shape.

High-Speed Steel Forming Tools. At the present time, when
high-speed steel is so extensively used in reducing the cost of many
machine operations, forming tools are also made from this metal.
The high-speed steel tools may be hardened by heating them in

Fig 189.

A'rangement of Two Forming Tools for
Special Work

126

TOOL-MAKING

specially constructed furnaces, or in a crucible of red-hot lead, and
then dipping them in oil, but more satisfactory results are obtained
if they are pack hardened by the method already described.

After pack hardening the tool, it may be necessary to draw the
temper somewhat; this will not be needed if the tool is strong and is
not to be subjected to severe use. If, however, the tool is weak or
has weak projections, it will be found necessary.

MILLING CUTTERS

Milling machine cutters are made in two different forms — 9olid
and wiih inserted teeth. It is customary in most shops to make cutters
up to 6 or 8 inches in diameter solid, and above this size with inserted
teeth.

Use of High-Speed Steel. At the present time, when rapid
reduction of stock is necessary, it is the custom in many shops to

Fic- 100. Side View and Seetion of Side Millinc Cutter

make many of the milling machine cutters from high-speed steel.
If this steel is properly annealed, it is easily worked to shape; but
much better results are obtained if the tools used in cutting it,
both in the lathe and milling machine, are made from high-speed steel.
High-speed steel milling cutters may be heated for hardening
in the specially designed furnace shown in Fig. 23, Part I; but if so
treated, they must first be pre-heated in an ordinary fire to a low
red heat, as the sudden expansion due to rapid heating would rupture
the steel and spoil a valuable tool. When uniformly heated to the

TOOLrMAKINQ

127

TABLE VI
Cutting Edges for Milling Cutters

DlAMBTBII OV

Cvrram

(in.)

No. or CVTTINO

Edgv

DlAMBTSm Of

Cvmm

(in.)

No. or CvmMO

10 or 12

3i
4

6
6

20
24
26
28
30
32

proper temperature, they should be plunged into raw Unseed oil or
cottonseed oil. Here again, as in the case of forming tools, much
more satisfactory results are obtained if the cutters are pack hardened.

Although many shops have adopted high-speed steel for most
of their milling cutters, and some shops use nothing else, yet many
mechanics claim that for cutters
of intricate form which must
retain a fine finishing edge, high-
carbon steel gives better results.
But if they use the latter steel
for such cutters, yet for all
roughing cutters and for those of
ordinary form where fineness of
cutting edge is not material, they
use high-speed steel.

Solid Straight Cutters. When
making solid cutters, it is advis-
able to use steel somewhat larger
than the finish diameter of the
cutter. A hole should be drilled in the blank A inch smaller than the
finish size of the hole, and the outside surface turned off. After
annealing, the blank should be put in the chuck on the lathe, the
hole bored, reamed to size, and recessed as shown at C in the sectional
view of Fig. 190. The piece should then be placed on the mandrel
and turned to the proper diameter and length.

Milling Teeth. The teeth should be cut in the universal milling
machine, or in. a milling machine provided with a pair of index centers^
The number of cutting edges for solid milling cutters varies 9om^

Fif. ISil. Diagram of Cutter wiUi
NegHtive Rake

128

TOOL-MAKING

Fig. 192. Form of Cutter for Semicircular Slot

what according to the nature of the work to be done, but for general

shop use the numbers estimated in Table VI will be found satisfactory:

For most work it is desirable to have the faces of the teeth radial,

Fig. 190. However, when milling cutters are made to run in the

direction of the feed or on to
the work instead of against it»
the teeth should be given a
negative rake (cut ahead of the
center), as shown in Fig. 191,
as this has a tendency to keep
the piece being milled from
drawing toward the cutters.
For cutters to be used in sink-
ing a semicircular slot in such a piece of work as is shown in Fig. 192,
the teeth should be cut back of the center.

When cutting the teeth, it is necessary to use a cutter that
gives sufficient depth of tooth to provide a receptacle for chips, and
also gives a form that supports the cutting edges. A cutter may be
used that will produce an angle of about 50 degrees between the
face and the back of the tooth, as shown at A in Fig. 190. The cutter

should cut deep enough to

leave the lands about j^ inch

m width at the cutting edges.

Saws for Copper Work.

Metal slitting saws for use on

copper do not work well if

made the same as thQse used

on steel and most other metals.

The face of the tool should

have a rake of from 8 to 12

degrees, and the sides of the

tool given clearance^ as shown

sectionnn fi 1—.^ in Fig. 193. As such saws

Fig. 193. Form of Cutter Uwd for Copper ^rc usually made thicker at

the circumference than toward the center hole, there b little

trouble from their binding the work.

The pitch of saws for use on copper should be considerably
coarser than for those used on the harder metals. For saws of

TOOL-MAKING 129

ordinBry size, the teeth should be spaced nearly or quite 1 inch
ftpart; for instance, a saw 4 inches in diameter should have l?teeth.
Gnndinj iht IIiAe to Size. It is customary to ream the holes
in milling cutters to siie, and it the cutter contracts in hardening,
the holes are brought to size again by lapping with a lead or cast-
iron lap, by means of oil and emery. This operation does not,
however, , provide for the enlarging of the hole. While expansion
it does sometimes happen, and. U a con-

ng. IM. Ty^r4l SH Up (at Grtndiac ■ Cutwr

sequence, the cutter dues not fit the milling machine arbor and
cannot do as good or as much work as it should.

The necessity of having a correct (5t on the milling machine
arbor makes it advisable to ream the hole of the cutter with a reamer
about .005 inch under the size of the arbor, and to finish by grinding
after the cutter is hardened. When grinding the hole to size, the
cutter may be held in a chuck and ground with a small emery wheel,
using the internal grinding attachment as shown in Fig. 194. This
attachment is so designed that it may be swung out of the way when
gaging the size of the hole. Fig. 195.

t30 TCMDL-MAKINa

Grinding Siumhhrt. After grinding the hole to aixe, it is ad vimble
to grind the shoulden on e«ch side of the cutter, straight and true
with the hole, in prder to prevent any possibility of sprin^ng the
miiling machine arbur because of untnieness on the part of the
cutter, and to prevent any possibility of the cutter running out of
true. The shoulder, or boss, referred to is shown in A, Fig. 190.

There are two methods of gnnding the shoulders. By one
method, the outer shoulder and the hole are ground Bt the same set-
ting; if thb is done properly, this shoulder will he true with the htde.
The chuck is then removed from the grinder, and a faceplate having
an expanding jdug is put in its place. The shoulder that has been
ground is placed against the faceplate, with the expanding plug in
the hole of the cutter. The odier shoulder may be ground after the
plug is expanded until the cutter is held rigidly in place against th«
faceplate, which vhovld run perfectljr true,

TOOL-MAKING 131

By the other method, both shoulders are ground while on ko
arbor, which is necked down each d of the cutter. Fig. 196.

Allowing the wheel to traverse the whole length of the shoulder
but not cut into the arbor,- as when an ordinary mandrel is used.

Orinding Teeth. In order to get the best results rrom a millinf
tter, it b necessary to use a form of grinder having some means of

132 TOOL-MAKING

properly locating each tooth as it is presented to the wheel. The usual
•mngement is a finger adjustable to the proper height to produce the
required amount of clearance, which is about 3 degrees, as shown at
B, Fig. 190. With this amount of clearance, the
cutter worksfreely and retains its edge; if more clear-
ance is given, the cutter is likely to chatter, and
the edges of the teeth will becom? dull rapidly.

Fig. 197 shows a cutter in position for grinding
the teeth; it will readilybeseen that the tooth being
ground rests on the centering gage E, which can be
adjusted to give any desired amount of clearance
to the tooth. For grinding the teeth on the aide of a
milling cutter, a small emery wheel may be used in
order to get the necessary amount of clearance with-
out touching the tooth next to the one being ground.
If a grinder is used which will take a cup wheel.
Hi. im. SectiiH ^V' '^' ^'"^ whosc table can be turned to bring
^$£Sr^™ the cutter in the position shown in Fig. 199, a form
of clearance is given which is more satisfactory than
a clearance ground with a small wheel. With the cup wheel the
line of clearance is straight, while with the small plain wheel it
it hollowed out, and as a consequence the cutting edge is weak.

QhnfUni Millinc CnttB

SUe Milling Cutter. Cutting Teeth. The form of cutter shown
in Pig, 190 is known as a side milling cutter. Wben cutting teeth
gn the Bides, it is necessary to put the cutter on a plug whose uj^r

TOOL-MAKING

end does not project much above the top face of the cutter; thb
plug may be made straight and held in the chuck on the end of spindle
in the spiral head. Such a plug is shown in Fig. 200, inserted in the
cutter. If many cutters are made with teeth on* the sides, it is advis-
able to make an expanding
arbor, Fig. 201, whose shank
fits the taper hole in the spin-
dle of the spiral head. When
milling'the teeth on the sides,
the index head must be in-
clined a little so that the side
of the mill will stand at a
small angle from the hori-
zontal, in order that the lands
of the teeth may be of equal
width at each end. The
amount of this inclination can-
not readily be computed . It is formed by cutting first one tooth , leav-
ing the cut somewhat shallow, then turning to the next tooth. After
cutting the second tooth, the change in inclination will be apparent.
Hardening* When the teeth are cut and the burrs removed, the
diameter and length of the cutters may be stamped as shown in
Fig. 190. The cutter is now ready for hardening. To harden success-
fully, it is necessary to have a low, uniform red heat; the teeth must
be no hotter than the portion between the hole and the bottom of the
teeth. If held toward the light, there should be no trace of black in
the interior of the cutter. When a uniform heat, no higher thart is
necessary to harden the steel, has been obtained, the cutter should

Fis. 200 MIlKnir Cutler Mounted on Pluf

Fie. 201 . Typical ExpandiDg Arbor

be plunged into brine from which the chill has been removed, and
worked around rapidly in the bath until the singing has ceased. It
should then be removed from the brine and immediately plunged
into, oil and allowed to remain there until cold. When cold, the

134 TOOL-"MAKING

cutter should be Ukeii from the oil arul heated sufficiently to prevent
cracking from internal strains, then brightened, aitd the temper drawn
to a straw color.

Spiral Milling Cutters. It b customary in most machine shops
to make alt milling cutters of more than J-inch face with teeth cut
spirally as in Fig. 202. The amount of spird given the teeth varies
in different shops and on different classes of work.

The ohjectof spiral teeth is to maintain a uniformity of cutting
duty at each instant of time. With teeth parallel to the cutter axis,
the tooth, on meeting the work, takes the cut its entire length at
the same instant, and the sprin^ng of the device holding the work
and of the cutter arbor causes a jump to the work. If the teeth are

cut spirally, the cut proceeds gradually along the whole length of the
tooth; and after it is started, a uniform cutting action is maintained,
producing smoother work and a truer surface, especially in the

Milling cutters may be cut with either a right- or a left-band
spiral or helix, although it is generally considered good practice to cut
a mill having a wide face with a spiral! that will tend to force the
cutter arbor into the spindle rather than to draw it out; then, again,
it is better to have the cutting action force the solid shoulder against
the box, rather than draw the adjusting nut against the boic.

Where two very long mills are used on the same arbor and it is
found necessary to cut them with a quick spiral, one cutter b some-
times made with a right-hand q>iral and the other with a left-haad

TOOL-MAKINO

spiral, in order to equalize the strain aiiU to reduce the frict
ing from the shoulder of the spindle pressing hard again)

Special care should be taken in cutting spiral d
to see that the work does not slip. When a
cut has been taken across the [ace of a cutter,
it b bent to lower the knee of the milling
machine, thus dropping the work away from
the mill while coming back for another cut;
the knee can then be raised to its proper posi-
tion, which is determined by means of the
graduated collar on the elevating shaft of
the machine.

As it is important that the face of the
cutting tooth be radial and straight, it will
be found necessary to use an angular cutter
of the form shown in Fig. 203, since cutters
of this form readily clear the radial face of
the cut and so remain sharp longer and
produce a smoother surface to the face of
the tooth than an angular cutter of the
form used for cutting teeth which are parallel to the cutter axis.

The angular cutters for spiral mills are made with either 40
d^rees, 48 degrees, or 53 degrees on one side, and 12 degrees on the
other. By setting the
cutter, as shown in
Fig. 203, 90 that the dis-
tance A is one-twelfth
the diameter, the fice
cut by the 12-degree
side of the angular cut-
ter will be nearly radial
for the usual propor-

cutting the teeth of a
spiral cutter must be
made before turning the spiral bed to the angle of the spiral.
Niekid Teeth. Spiral cutters with nicked teeth. Fig. 204, are
espenally adapted for heavy milling. As the chip is broken up, a

136

TOOL-MAKING

much heavier cut can be taken than would be possiUe with an ordi-
nary cutter. The nicking may be done as follows: An engine
lathe is geared to cut a thread of the

required pitch — two threads to the
inch will he found satisfactory — and
with a round-nosed tool i inch wide,
a thread is cut of a depth that will
not grind out before the teeth become
too shallow to allow further grinding.
I This thread should be cut before mill-
'" ing the spaces to form the teeth.

MHIins Cutters with Interlocking Teeth.
When two milling cutters of an equal diam-
eter are to be used on the same arbor in such
a manner that the end of one cutter is against
the end of the other, the corners of the cutting
teeth are likely to break away, leaving a pro-
jection — or fin — on the work, as shown in
Fig. 205. In order to overcome this, part of
the teeth are cut away on the sides of the
cutters; that is, a tooth is cut away on one
cutter, and the corre<iponding tooth on the
other cutter is left full length to set into the
recess formed by the cutting away of the
tooth. In some shops it is customary
to cut away every other tooth; while
in others, two, three, or four teeth will
be cut away and an equal number left.
Fig. 206 represents a pair of mills hav-
ing every other tooth cut away, while
Fig. 207 represents a pair having four
teeth cut away.

In order to cut away the teeth
to make a cutter with interlocking
teeth, the cutter should be placed on a
* «Mk pluKO''ftn*'tpandingarbor,asdescribed
for milling teeth on the sides of side
milling cutters. By means of a millmg

TOOL-MAKING

137

cutter having the proper width, the teeth may l>e milled away,
although, in the case of a cutter having several teeth cut away,
Fig. 207, it b well to use a narrow cutter, and after taking one cut,
to turn the index head so that the next tooth is in position. This
should be continued until the desired number of teeth have been
cut away, after which the index head should be turned to pass over
the required number of teeth, and the operation repeated.

It is necessary, when making cutters with interlocking teeth
(sometimes called dodged teeth) that the milling be deep enough to
prevent the corresponding tooth on the other part of the cutter from
striking the bottom of
the recess. The parts of
the cutter should bear
against each other on
the shoulders, or hubs.

Cutters for Milling
Slots. An excellent form
of cutter to be used for
such work as milling
slots can be made as
shown in Fig. 208. This
form IS less expensive
than one having interlocking teeth and answers the purpose as well.
It IS necesssary to make an eccentric mandrel of the design shown in
Fig. 209, having the eccentric centers on opposite sides of the regular
centers. The two pieces which make the cutter should be cut from
the bar long enough to Rnish the thickness of the heaviest part

Fig. 208. Milling CuitCsT for Slots

Fig. 209. Eccentric Mandrel for Slot Cattera

A A, Fig. 208. The hole is made i^ inch smaller than finish size,
the outside surface turned off, and the pieces annealed.

After annealing, the hole is made the size desired for grind-
ing. One of the pieces is then placed on the eccentric mandrel,
forced on until the side that is to be beveled is exactly in the center
of the mandrel. The side B may be machined with the mandrel

las TOOL-MAKING

running on the n^Ur centers, white the beveled side, must be
machined with the mandrel running on the eccentric centers. When
the arbor is running on these centers, a distance half-way between

3- i ■ J

the two ends runs true; it is at this point that the side of the blank
to receive the bevel should be located, as shown in Fig. 210, provided
the eccentric centers are of an equal depth. When the two parts 0(
the cutter have been machined to shape, they should be so placed
on a stud that the two beveled sides will be next each other, Fig. 208,
the thinnest part of one next to the thicltest part of the other. TTie
pinhole should now be drilled and reamed for a ^-inch pin, which

should be inserted. The blank la next placed in the viseon theahaper
or planer, and the spline slot cut as shown. It is now ready to be

T(X)L-MAKINa 139

AFl<-r the cutlt-r 1ms hven luirdened, the beveled sides are ground
true, the halves put together, the hole ground to size, the cutter
ground to thickne^, and tlie teeth ground for clearance. If it is
found necessary to increase the width of the slot, that caa be done
by shimming between the two parts of the cutter with paper or thin
. sheet metal; the design of the cutter allows this to be done without
leaving any fin in the slot.

Angular Cutters. Directions for making angular cutters are
practically the same as those given for making solid straight cutters,
except that the desired angle jnust be given.

When milling the spaces which form the teeth, the index head
is set at an angle that will cut the edge of the tooth
..f un equal width its entire length. After removing
the burrs, the cutter may be hardened and tempered.
Tl)e hole should be ground to size aiul the sides
gniiiud true with the hole. It should then be placed
on a mandrel or stud, and the teeth groynd for
clearance Fig. 211 shows the method used in grind-
ing the teeth of a mil! of this form.

Milling Cutters with Ins^lcd Teeth. When
milling cutters exceed (j or 8 inches in diameter, it fit- 3ii Brwa
is generally cheaper to make the body of cast iron or glVfSl'rJ"''
mucliirie steel, and to insert m the penpheiy teeth
made of tool steel or high-speed steel. There
arc a variety of methods fur holding the
tn'th in |>lacc. If the cutter is narrow, or
is lo he used as a side millmg cutter, the ,
grooves to receive the teeth may be cut i

straight {parallel to the cutter axis), Fig. 2!2. '
If the cutter face is awr one inch long, the
slots lo receive the Iccth should be cut in
such a manner that spiral teeth may be
used, as Khown in Fig. 213. .^* " iW^'Vw'i.'" ''"■

Ching HuktloHUi. Whileitisaeom- '^ulZi^,^:;'^:^^^^^
paratively eiiay matter to cut the slots ''"••^'^. BAWtJw.^f
spirally, it is dilTiciilt to make the teeth of a shape that will fit the
spiral slots without the aid ot special tools. Consequently, thealots
are generally milted at an angle lo the cutter axis, having the side

140 TOOL-MAKING

ihat (vrrespondit to the face or the tooth equidistant from a radial
hne at each end of the cut. The face of the alot at one end would
be ahead of the center, while at the opposite end it would be behind
the center; this gives front rake and negative rake, respectively.

The slots should be cut somewhat wider than would be neces-
sary were the teeth to be of spiral form. After turning to siie,
the faces uf the teeth may be milled spirally to make them radial
If the mills are intended For heavy work, the teeth should be nicked.
The cuarse-pitch thread should be cut before the teeth are milled
spirally.

Grinding Teeth. After
being hardened, the teeth
may he put in place and
fastened, when they are
ready for grinding. The
emery wheel for grinding
milling machine cutter
teeth should be of the
proper grade as to hard-
ness and coarseness; if the
wheel \i very hard or fine,
it will be likely to draw
the temper at the cutting
edges of the teeth; the
Fii. sn. spfjw Tym ot^innfmci-ToniK emery should not be
<■..,!-., ^ fl~-w'M."inri'=rt,.. c.™,«.,. coarser than No. GO, or

If the face of the wheel is glazed, remove the glaze with a piece
of emery wheel somewhat harder than the wheel in use; this not only
removes the glaze, but makes the surface of the wheel more open and
lesi likely to glaze. The emery wheel should run true; its face should
nol exceed 1 inch in width. Generally speaking, the softer the
emery wheel, the faster it should run, but the peripheral speed
should nut exceed 5,000 feet per minute.

Fastening Teeth, There are several methods for fastening the
teeth in this form of cutter, any one of which gives satisfaction if
the work is well done. The method illustrated in Fig. 214 is in use
in the works of the Pratt and Whitney. Company, and of the

TOOL-MAKING

141

Becker Milling Machine Company. In this design, between every
second pfur of teeth a hole is drilled and reamed taper to receive

the taper pb, after which the slots

are cut with a thin cutter. When the
cutters are in place, the taper pins are
driven into the holes, thus locking the
cutters. To remove the cutters, the

A method of fastening cutters
used by the Morse Twist Drill and
Machine Company, of New Bedford,
Massachusetts, is shown in Fig. 215.
In this case the stock between every
second pair of teeth is milled away,
not so deep, however, as the slots
for the cutters. Wedge^haped
pieces of steel are fitted between
the teeth as shown. When these
are drawn to place by means of
fillister head screws, they bind
the cutters very securely. It the
wedge-shaped binding blocks
touch the bottoms of the slot
they will not hold the cutiei
securely in place.

The cutter shown in Fig.213
indicates the method used by the
BrownandSharpeManufacturing
Company. The teeth are securely
held by taper bushings, which are

drawn to place by screws, as shown g

at A, Fig. 216. To remove the /

taper bushings the screw A is fii iir sn-ikpn o( 5i.i»(.ni Kwwiy
removed and a plug fi inserted. To insert a tooth, set blade in posi-
tion and drive bushing into place using set C; then insert screws A.

Keyways. To prevent milling machine cutters from turning
on the arbor when cutting, it is necessary, especially when taking
heavy cuts, to have keyways cut as shown in Fig. 217 and Table VII,

142

TOOL-MAKING

TABLE VII
Dimensions of Standard Ke3ways for Cutters

(LaiUra refer to Fig. 217)

2>iAMmB (D)

Wion (IT;

Dbpth id)

RAoroa (ft)

On)

do:)

(ID.)

(in.)

020

030

Htoi

035

lAtoi

040

lHto2

050

060 •

2iV to2|

060

2A to3

060 .

The arbor, of course, must have a similar slot to receive the key.
It will be noticed that the dimension d refers to the diameter of

the hole in the cutter,
and not to the diameter
of the cutter. A key-
seatmg machine equipped
with the proper tools,
furnishes a verv satisfac-
tory method of cutting
key ways in milling ma-
chme cutters, but all
shops are not provided
with such machines. The
form of tool shown in
Fig. 218 (A) is exten-
sively used for such pur-
poses on the planer, or
shaper, and works well if
everythmg about the ma-
chine is in good condition. If, however, there is any looseness in any
of the parts, or any backlash m the vertical feed screw, the form
Fig. 218 (B) will be found more satisfactory, as it is fed up in the
operation of cutting, and the backlash cannot prove a source of
annoyance. The writer has found this form of tool satisfactory on all
interior cutting on the shaper and planer It is necessary to clamp
the tool head so that it cannot rise on the return motion of the planer

Fi«. 218. Forms of Keywiiy Cutters for Planer

Shaper

TOOL MAKING 143

In shops where many cutters having holes at the same size are
made, a saving of timtf will be etTetrted, if there Ja a draw-broaching
machine, by bruaching the keyway. A number of cutters having
the same size of arbor hole can be broached in a fraction of the time
necessary to cut them on the planer or shaper with the key-dotting
tool shown; when, however, but one cutter is to have the keyway
cut, the planer method may prove to be quicker.

As all stock is not perfectly homogeneous, tools of the description
shown will not always cut an absolutely straight slot. For most
purposes, the amount of variation need not be considered; but when
an absolutely straight cut is necessary, the fonn of tool shown in

Fig. 213(0, is used. The portion marked < is made .001 or.(H)2inch
smaller than the hole throuRh which it is to pass. The cutter is set
in a slot which passes through the tool as shown, and is fed into
the work by means of the pointed feed screw.

Formed Cutters. As used by the Brown and Sharpe Manufactur-
ing Company, the term formed cutter applies to cutters with teeth
so relieved that they can be sharpened by grinding without changing
their form. The term can be applied, however, to any cutter which
cuts a form, regardless of the manner in which the teeth may be
relieved. Fig. 210 represents a formed cutter. Formed cutters are
used in many shops where work of irregular shape 'is milled in large
quantities, as in sewing machine, gun, bicycle, and automobile shops.

144 TOOL-MAKING

If many formed mills are to be made, it is advisable to procure
or make a machine specially designed tor relieving — backing off— the
teeth. As such machines are heavy and rigid, large cutters may
be relieved and a smooth cut obtained, which is not possible with a
light machine.

Backing^Off L<Uhe AttachTnentf. Altliough this style of cutter
can be made to better advantage in a shop equipped with machinery
deigned especially for this class of work, an ordinary engine lathe

can be converted info a backing-ofT lathe for relieving or backing off
the cutters. Thereareseveralcommercialdevicesfor the work; one
comparatively inexpensive fixture is known as the "Bslzar" backing-
off attachment, Fig. 220; another arrangement consisls simply of an
eccentric arbor operated by a hand lever; or. a stud may be screwed
into the faceplate of a lathe and the cutter placed on this stud in
a position that allows the teeth to be given the necessary amount ol
clearance.

TOOL-MAKING r4S

When backing olT the teeth of cutters whose faces do not exceed
one inch m width, the Balzar backing-olT fixture can be used to
advantage. This device is held between the centers of a lathe in

the ordinary manner, the backing off being such that the cutter can
be ground without alteration of shape. The tool in so constructed
that 't is only necessary to place the cutter upon the arbor in the
ordinary' "'ay. Place the arbor on the lathe centers as shown, start
the lathe, and feed the forming tool in by the cr(«s-feed screw in
order to take the desired cut. in the same manner as in plain turning.
The ratchet connected with the arbiir and actuated by the pawl,
contains orrlinaril)' 3f> teeth, and the stroke can be set to back off
a cutter with 9, 12, 18, or 36 teeth.

Backing Off by on Eccentric Arbor. An arbor may be made
having a pair of centers located to give the cutter tooth the required
amount of clearance; such an arbor is shown in Fig. 221. The
eccentric centers are shown at the sectional portions at the ends.
The amount of eccentricity depends somewhat on the size of the cutter
to be backed off, but for cutters not exc'eeding 'i inches in diameter,
from A to i inch will give excellent results.

1 he screw at the end of the arbor should be of a line pitch, about
12 threads per inch for arbors one inch in diameter. The object in

cuttinc a fine-pitch thread is that the cutter, being backed off, cai
be held more securely with the same amount of force exerted ii
tightening the nut; again, the depth of the thread is not so great ai

1^6

TOOL-MAKING

Fig. 223 Cutter Blank with
Straight Grooves

for a thread of coarser pitch, and, as a consequence, the plane portion
at the end of the arbpr; which is made the size of the bottom of the
thread, can be left large enough to get in a center hole of good size

having J-inch eccentricity.

The spline should be cut at least |
inch wide and about i inch deep; the
walls of the cut shoi^d be parallel in order
that the screws shown in Fig. 222 as pass-*
ing through the collar and entering the
slot in the arbor, may have a good bear-
ing. These screws are to keep the collar
from turning when the necessary force
is applied to the nut for fastening the
cutter in place. The collar on the oppo-
site side of the cutter has a spline cut the same width as that in the
arbor, and it is held in position by a spline, as shown. The cutter
itself cannot be held by a spline, as it is necessary to move it each
time a tooth is brought into position for backing off.

The cutter blank, when machined, is given the desired shape
by means of a forming tool. If there is much variation in size, the
shape should be roughed out before using the forming tool. After it
has been machined to the desired size and shape, the cutter should
be placed between the centers of the milling machine and a number

of grooves cut its entire length. The
number of grooves must correspond to
the number of teeth the mill is to have;
the grooves cannot be cut to finish
width until after the teeth are backed
off, because the forming tool cuts a trifle
deeper at the point of contact, making it
necessary to mill a small amount from the
face of the tooth after backing off. The
grooves are sometimes cut with a thin
milling cutter, or a metal slitting saw |
inch thick. When a groove of this
description is cut, the cutter has the appearance shown in Fig. 223.
A groove of this form makes more work for the operator than one cut
as shown in Fig. 224, in which the distance -across the tops of the

Fie 224. Cutt4>r Blank with

Grooves Made by Angular

Cutter

TOOL-MAKING U:

tee^ 'a decrused by u&ing an angular cutter of the shape showD ii
Fig. 225.

After the grooves have been maile, the cutter is placed on thi
eccentric arbor, which is held between the centers of the
lathe in the ordinary matiner. A fonnitig tool that will
produce the desired shape of tooth is placed in the tool
post; the top face of the tool must be 5et at the exact
height of the center of the lathe in order to produce the
proper shape. Fig. 226 shows an eccentric arbor in a
lathe in position to back uR the teeth in a fiirnieil mill.
The arbor is operated by means of the lever, and is
entirely independent of the spindle in its action, the eccen-
tric centers beiiif; placetl on the centers of the lathe, and
the necessary motion given by means of the lever which
strikes the carriage at the end of the stroke, hi order
to avoid bruising the lathe, a atrip of leather is attached
to the lever, as shown.

To set the cutter tooth iu the proper location l>efore
backing off, a piece of thin sheet metal is placed on the lElSJ^of
top face of the tool, as shown in Fig, 227. The lever is Cuii/r'

148 TOOWWAKING

brought down upon the cairiaKe, the tooth of the cutter is brought
down upon the sheet metal, und the nut is tightened. The tooth to
be backed otf is the one bdow that set to the thickness of the strip
above the tool. The objei't in raising the tooth a given distance
above the Face is to prevent striking tbe tool Bt the end of the
stroke. This operatiou must be repeated for the setting of each
t«oth before backing off. The forming tool is fed' by means of the
cross-feed screw; a tooth is backetl off nearly the desired amount,
leaving a little for a finish cut; the tool b withdrawn, the nut

loosened, and tlie cutter turned on the arbor to bring the next
tooth in position to be backed off, this operation being repeated
until alt the teeth are backed off alike. The' amount of backing otT
must be determined by the cross-feed stop or by a graduated dial
on the cross-feed screw. After the roughing cut has been taken on
all the teeth, the forming tod should be aharpened by grinding
Or by oil-stoning, and the finish cut taken on the teeth.

Backing Off by Stud in Faceploie. Another method of backing
ofT cutter teeth is shown in Fig. 22S. A stud b screwed in the face-
f^ate of a lathe near tlie outer edge, as shown. The cutter, which
must be a fit on the stud, is clamped by means of the nut. The finger

TOOL-MAKING

149

A is movable in the slot in the stationary block B, which is so located
on the faceplate as to bring the tooth to be backed oft' into its proper
location, and to keep it from turning during the operation. The
forming tool is fed in gradually until the tooth is formed. The finger
is then disengaged from the space in the cutter, which is revolved by
means of the set screw until the next tooth is in position. Each tooth
is machined separately; that is, the forming tool is fed in the required
distance for each tooth when it is in position, the cutter is turned
until the next tooth is in position, and the process repeated until
each tooth has been backed off. .In backing oft' cutters in this

Fig. 228 Set-Up for Backing Off Cutter on Faceplate

device, it is necessary to cut the notches (the spaces between the
teeth) somewhat wider than the teeth.

General Directions for Backing Off. When backing off the teeth
for clearance by any of the means described, it is first necessary to
form the blank, then to gash it or to cut the notches as described;
then to back off the teeth. After backing off, it is necessary to mill
the face qf the tooth back A inch or so, to cut away the "jump", as
it is termed, caused by the forming tool drawing in a trifle when it
first strikes the edge of the tooth.

Cutters of this description are shari>ened by grinding on the
face of teeth, as shown in Fig. 229.

Milling Cutters with Threaded Holes. It is often necessary to
make' milling cutters with threaded holes. This happens in the case

150

TOOL-MAKINO

of small angular cutters, and in many styles ot cutters for uae on
profiling (edge milling) machines.

The general instructions given tor making the other forms of
cutters Apply to those with threaded holes, except that instead of

reaming the hole to a given size, the thread is cut with a tap of the

proper she and pitch, or it is cliastxl in the lathe. After threading,
the cutter should he screwed on to a threaded arbor. Fig. 230 shows
an arbor of this description. The end A is threailed slightly taper-

Ing, for short cutters about .002 inch in one inch of length. On the
taper end of the arbor, a thread should be cut of a size that will not
allow the cutter to screw on the arbor quite the entire length; that
is, the cutter should overhang the threaded portion of the arbor ft

TOOL-MAKING 151

trifle, say one thread. This allows the outer end to be squared up
without mutilating the threads on the arbor. The reason for using
the taper end of the arbor when squaring the first end of the cutter
is that the shoulder b true with the thread in the cutter. After
squaring this shoulder, tfie cutter blank may be removed and placed
on the opposite end of the arbor with the side that has been squared
against the shoulder of the arbor.

This method of machining pieces of work having a threaded
hole, where it is desirable that the outer surfaces be true with the
hole, is applicable to all classes of work. The cutter may be
machined to length and shape un the straight end of the arbor.

Fly Cutters. The simplest form of milling machine cutter is
known as a fly cutter. It has only one cutting edge, but is particu-
larly valuable when mak-
ing but one or two pieces
of a kind for experimental
work, and when making
and duplicating screw-
machine and similar tools
of irregular shape. As
these cutters have but one cutting edge, they produce work very
accurate as to shape, but they cut very slowly and do not last so
long as those having more teeth. However, they are used on special
work, on account of the small cost of making, it is necessary to
hold the cutters in a fly cutter arbor ^ Fig. 231.

The cutter to be used in a fly cutter arbor may be flled to a
templet, giving the nceesiwry amount of clearance in order that the
back edge, or ^'heel", may not drag. If it is desirable to make the
impression in the fly cutter with a milling cutter of the regular fbrm,
the piece of square steel from which the cutter is to be made may be
held in the milling machhie vise, and the shape cut with the milling
cutter. The desired amount of clearance nmy be given by holding
the piece in the vise at an angle of a few degrees.

To make a fly cutter from the forming tool, the piece of steel
may be held in the fly cutter arbor in such a position that the face is
somewhat back of a radialline, as shown in Pig. 232. After hardening,
the cutter should be set so that the cutting edge will be radial, and
the clearance will be as shown in Fig. 233.

Fig. 231. Fly-Cuu«r Arbor

154

TOOL-MAKING

the teeth on the end of the mill are being cut, the spiral head is
turned until the cutter is in a horizontal position. The angular cutter
used should not have a very acute angle» or the teeth will be weak.

Fie 240. Spirmf End Mill
CouHnni of Btcker MiUiny Machine Company, Hyde Park, MatsaehusetlM

An 80-degree angular milling cutter will be satisfactory for
most work.

Spiral End Mills. It is sometimes advisable to cut the teeth of
end mills spirally, as shown in Fig. 240. As there is no support at
the outer end of this form of mill, it will be necessary to cut the
teeth of a spiral that will have a tendency to force the mill into the
collet rather than to draw it out. Fig. 240 represents a left-hand end
mill cut with a right-hand spiral.

End Mills uith Center Cut. This form of end mill is useful when
it is necessary to cut into the work with the end of the mill, and ^hen
move along, as in the case of dies, cams, and grooves. The teeth,
being sharp on the outside, cut a path from the point of entrance,
and, being coarse, allow a heavy cut, especially in cast iron.
Fig. 241 shows two views of an end mill with center cut.

After the teeth on the end have been cut with an angular, cutter,
a thin^ straight-faced cutter of small diameter should be run through,
close to the face of the cutter tooth, making a cut as shown at A;
this cut should be of sufficient depth to permit backing-off the inner

Fig. 24 r. Form of End Mill with Center Cut

edge of the tool, as shown at B. This clearance allows the mill to
cut away the slight projection left in the center of the mill when it
is fed into a piece of work, Fig. 242. >

TOOL- MAKING

155

T'Slot Ctittm. In cutting T-slots in various ptrts of maphines,
such a^ milling machine carriages, etc., it is necessary to use a form
of shank mill known as a T-slot cutter. Fig. 243
shows the ordinary fonn of T-slot, while Fig. 244
shows the.cutter. A portion of the stock below
the teeth is cut away, as shown at ^4.4 in the
sectional view. Fig, 245. This is necessary in
order to- back off the teeth on the sides of the
cutter for clearance, and to do away so far as
possible with unnecessary friction when the
cutter is working.

T-slot cutters are usually made i\ inch
larger in diameter than the size designated on
the cutting portion, to allow for sharpening;
that is, a nail! intended for cutting a slot
j inch wide is made j-fA^ or H inch in diam-
eter, unless intended for cutting a slot to given dimensions.

It is advisable to harden mills of thb descriptioi
length of the neck, especially if that is
of small diameter; for otherwise they will
be very likely to spring when in use.
After hardening.the neck should be drawn
to a blue color, while the cutting part
should be drawn to a straw color.

When grinding end mills, the shank fv '*' B«iipB8bMiMTyiHcia
in all eases should be ground first to fit

the collet or hdder, allowing it to enter far enough to key out
readily, but yet not enough to allow the shoulder above the tenon
to strike the shoulder in the collet.

l!^^ E2i*M?ll

After grinding the teeth for clearance on the diameter, the
t«eth on tbe end should be ground. Moat universal and cutter

156 TOOL-MAKING

grinders are provided with a fixture Tor holding the mill by the
ahank while grinding these teeth, Fig. 246.

Face Mlllint Cutters. This
(onn of cutter is used in milling
surfaces too large to be cut with
the ordinary form of milling cut-
ter held on an arbor passing over
the work. As the Full diameter of
the face of the cutter can be used,
it can have less than one-half the
size that would be necessary for a
sidemillingcutter. Asidemilling
'cutter 'must_ be double
the diameter of the sur-
face to be cut, plus the
diameter of the collar on
the arbor. For instance,
ifasurfaceas^,Fig.247,
were to be milled, it
would be necessary to
use a cutter somewhat
lai^er in diameter than
twice the height of the
surface plus the diameter
, of collar B; whereas, if a
face milling cutter of the
form shown in Fig. 248 were
used, the diameter need not
be much greater than the
heightof the face of the piece
of work being milled.

Generally speaking, cut>
ters of this description ate
necessarily of a diameter that
makes it adv&kble to oat
inserted teeth. The body
may be made of cast iron,
having a taper hole and key-

TOOL-MAKING

TABLE VIII
DimcniiinK of F*ce Mililnt CutUn ^

-a^-

"'^r

~™&fi-

12
12

an be KftdSy understood
Tb« letters ^,fi, and C

way, an<^ held in plac« on the arbor by

The teeth should be made of tool
steel and h&rdened, or of high-speed
steel, if the cutter is to be subjected to
rough usage. In either case, they can
be fitted to the slots by grinding on a
surface grinder, and held in place by
taper bushings and screws, as explained
under "Milling Cutters with Inserted
Teeth". The construction of the body
from the sectional view given in Fig. 249.
re present d iameter of cutter, w idth of face,
uiid number of taper of the hole, respec-
tively, while D represents the keyway.

Table VIII gives the dimen^ons of
face millinf* cutters of difTerentdiameters.

After the taper hole has been bored
and reamed, the body of the cutter
should be placed on a taper mandrel
fitting the hole, and the ends and cir-
cumference finished to size. It is then
put !n the vise ontheshaper or planer at
the proper angle, and the spline slot cut
to an equal depth at each end of the
Uper hole. The burrs having been "« "» »«iyorr«.
removed, the cutter should be placed between the centers
milling machme, and the slots cut for the teeth.

156 TOOL-MAKING

When the teeth are firmly secured in their proper places, they
should be ground for clearance, in accordance with the general
instructions already given for grinding other forms of milling cutters.

Arbors for Face Milling Cvtters. In Fig. 250 is shown an arbor
to be used in connection with face milling cutters. The shank A
fits the hole in the spindle of the milling machine. B is the body
which fits the taper hole in the cutter; this portion of the arbor has
a spline which fits a spline slot in the cutter. The screw C enters the
body of the arbor, and holds the cutter on the arbor. D is a nut
used to force the cutter off the arbor when It is necessary.

Stock used in making such an arbor should be strong and stiff,
and on thb account tool -steel ij^ generally used. With the ends
squared and the circumference roughed out, one end should be run
in the steady rest, and the screw hole in the end drilled and tapped;

Fig. 250 Arbor for Face Milling Cutter

after which the arbor should be countersunk at the end to furnish a
center for use in turning and finishing. If necessary to harden the
end of the tenon, that should be done before finish-turning the
arbor, to prevent springing when heating. When the taper has been
turned to fit the hole in the milling machine spindle, and, on the
opposite end, to fit the cutter, the thread can be cut for the nut D,
after which the arbor is cut for the spline as already explained .

The result will be more satisfactory if the two tapers are left a
trifle large until after making the spline cut, and are then ground
to fit. Although the spline is intended to fit snugly in the slot in the
arbor, the fit should not require pressure enough to endanger the
trueness of the arbor when it is pressed to position.

MILLING MACHINE FIXTURES

When producing work by milling operations, it is necessary to
use good cutters; it is equally necessary-te employ suitable means of
holding the work. It is a waste of money to make costly cutters and

TOOL-MAKING 159

to purchase a strong, heavy machine, and then to use a weak, poorly
designed holding device. When unsuitable holdmg fixtures are used,
accurate work cannot be produced unless extremely slow feeds are
employed, and even then it is many times impossible. In fact, the
designing of fixtures to hold work in the milling machine calls for as
great a display of ingenuity as the designmg of any class of tools
used in the shop.

Essential Features. Years ago almost all pieces produced by
the milling machine were purposely left large in order that they might
be brought to exact size by filing. Today most pieces are milled to
finish size, thus doing away with the costly operation of filing. But
in order to produce work of the desired accuracy, cutters must be
used that are of the right shape; machines must be provided that are
strong, rigid, and easily operated; holdfasts must be employed
which will hold the work and insure its being presented to the cutter
in such a manner that all pieces will be alike, so that perfect inter-
changeability of parts will be secured. This is impossible with light
fixtures, as they will spring, and not only will the sizes vary, but the
surface of the work will be covered with chatter marks.

The fixture must be rigid and strong, and the holding devices
must be of a design that allows rapid handling of the work. All bear-
ing and locating surfaces and points must be accessible, for the sake
of ease in cleaning, as dirt, or a collection of chips, at times the presence
of even one chip, might change the location of the piece to an extent
that would prove fatal to the work.

Most fixtures of this kind are made from cast iron, and as this
b a cheap metal that is easily shaped, it is possible to supply a
sufEcient amount to insure necessary rigidity. For fixtures that
are to be used over and over, it is advisable, generally speaking, to
supply seating and binding surfaces of hardened steel.

Simple Angle Iron Holder. When designing fixtures, plan to
have the strain Incident to binding and cutting the work come,
if possible, against the strongest part. Fig. 251 shows several holdmg
devices. A is made in the form of an angle iron. The binding and
the cutter strain both come against the rigid part. If the fixture
were reversed, the cutter strain would come against the strap, and it
would be found impossible to produce work to gage if heavy cuts or
moderately coarse feeds were employed*

160

TOOL-MAKING

MUliiig Machine Vises. UnuU Type, In the same figure, at
B, is shown a portion of a milling machine vise, the work being held
between steel jaws. If the work were of a character that made it
possible to use jaw» Q^nding but little above the top of the vise, it

Work

m. ill dM

Fig. 251. Forma of Milling Maohine HoJdfMtt

would not be necessary to use heavy ones; but in the illustration,
the jaws extend considerably above the top of the vise, and even
heavy ones would spring, or would draw away from the vise at the
bottom, thus throwing the work out of true. To prevent this, th^
are made of the form shown, and bear on the top of the vise.

TOOL-MAKING 161

Taking Care of the Burr, Whten pieces arc milled, a burr is thrown
out, as shown at C. At times, this burr will bear against the bearing
surfaces of the fixtures, and throw the work out of true; and.it will
also be pressed into the work, thus mutilating and spoiling it. Fre-
quently these burrs are removed by filing or grinding. At times this-
seems an unwarrantable expense, as subsequent operations would
cut them away at no expense; under such conditions, it is possible
to cut into the bearing surface and remove enough stock to provide
a place for the burr, as shown at D.

Use qf Extra Jaws. When it seems advisable to hold work in
the vise, and the opening is not sufficient to take in the piece, the
jaws may be made as shown at E.

Milling Vise Operated by Compressed Air. A milling machine
vise that is very satisfactory for many classes of work is opened
and closed by compressed air, which is carried to the various machines
in pipes. When compressed air is so used, it is often further employed
to clean the jaws. This operation requires a piece of flexible hose
having a suitable valve which can be opened so that the chips and
dirt can be blown from' the jaws. By this method it is easy to get
rid of small chips in places hard to reach with a brush. In fact,
compressed air is many times used in cleaning vise jaws where the
vise is opened and closed by meaiis of a screw or cam, the air being
automatically turned on as the jaws open.

Cam^. When a cam will fasten the work to the fixture strongly
enough, it proves a rapid method, and one that is often employed.
At Ff Fig. 251, is shown a fixture for holding bolts the heads of which
are to be straddle-milled. One cam binds two bolts, and as three
cams are provided, six bolts may be milled at a time. The fixture is
so designed that the cam handles are at the front of the fixture rather
than back of the cutters, as in this position the operator's hands
would be in danger. The cutter pressure is against the solid part of
the fixture, thus insuring rigidity.

Screws. At times cams do not prove satisfactory, and it is found
necessary to use a screw. Screws are slow of operation, as it takes
a long time to turn them back and forth sufiSciently to bind or free
the work. To facilitate matters, a slotted washer G, Fig. 251, is
sometimes provided, and a screw which passes through a hole in
the work is used. By this means it is only necessary to give the

TOOHHAKING

'Fi|. :i3. £«i-UpfDrMULiD(S1^lunaEiidal

TOOI-MAKING 163

screw a part of a turn in order to bind or remove the washer thus
giving a very quick action.

WedfCiiShaped Keys. When it is necessary to place the .binding
device on the under side of a fixture or in some inaccessible place, a
wedge-shaped key, as shown at H, Fig. 251, proves satistsetoiy.
It holds the work solidly on to the seating surface, and is quickly
and easily operated.

Special Holders. In Fig. 252, at A, is shown a piece of work
whose ends are milled square. As the sides are machined on a slight

FtltM. BM-Upan V«UulMUUitMMUiH<orMillin(AiilaBi>lHliSUF«rC(i<nn
C'tmi 'f Bit" Uiaini Muclliiu Cnira-iv. Mydi Part. MouscAwu

taper to the axis of the piece, it was necessary to hold the wwk as
shown at B, and use an end milling cutter.

In making fixtures of the kind -under connderation, the designer
should bear in mind that the simplest form which will insure desired
results at the minimum cost is the best. Complicated fixtures ^ould
always be avoided, it a simple one will answer.

Fig. 253 shows a method of holding a spindle and milling a slot
across the end. The work b held in a fixture made in two parts, and
the cut is taken by feeding the knee vertically by means of the auto

164 TOOL-MAKING

matic vertical feed. With a fixture of this description, the ends of
long pieces can be milled as shown.

Holders for Vertical Milling Machines. 'Fig. 254 shows a
fixture for holding work in a vertical milling machine, by the use of
which the process of milling is continuous. After a piece is milie«l,
it is removed and another put in its place while other pieces are being
milled. For many jobs of flat milling this method is to be recom-
mended as there is no lost time.

The problem in the up-to-date shop is to turn out all the work
possible in a day with the minimum expenditure for labor. By this
method of milling, the machine is cutting constantly, and the entire
time of the operator is employed in taking out, putting in, and gaging
the work. This is not the case where a man has several milling
machines of the ordinary type to tend; for then the time of the
operator is wasted when he walks from one machine to another,
and the time of the machine is wasted when it lies idle and un])ro-
ductive while the fixtures are being loaded and unloaded.

DRILL JIGS #

A drill jig is a device for holding work so that one or more
holes may be accurately drilled; the locations of the holes" may be
governed by hardened bushings (guides) through which the drills run

The design of a jig depends entirely on the shape of the piece
and the nature of the work to be done, but it must be such that
work may be placed in them and taken Out as quickly as possible.
The' fastening device should allow rapid manipulation, yet be
capable of holding the work without danger of a change of location.

The construction of drill jigs calls for as great accuracy as any
branch of the tool-maker's business, but no undue accuracy should
be indulged in. If the location of a hole is near enough when within
a limit of variation of ^ inch, it is a waste of time to attempt to get
it within .0005 inch; yet if the work is of such character that it is
necessary for the holes to be within a limit of variation of .0001 inch
or even closer, every effort should be made to locate the drill bush-
ings as accurately as possible.

Important Construction Features. Finifh, While the design
of the jig and the character of the work to be drilled must necessarily
determine the method of construction, a few general directions may

TOOL-MAKINO 16$

not be amiss. The amount of finish given the exposed surfaces of a
jig must be determined by the custom or requirements of the individ-
ual shop. In many shops it is not considered necessary or advisable
to finish the surfaces any more than to allow of their being wiped
without the waste sticking to the jig.

Under other conditions the surfaces are machined as smooth
as possible, and the surface finbhed by placing a piece of }- or j-inch
wood dowel in the drill-press chuck, so that the dowel projects }
inch or so from the chuck. The surface of the metal b covered with
a thin coating of oil and fine emery, and the dowel, revolving at high
speed, is brought down upon the surface, allowed to run for a few
seconds, raised, and again lowered so that it cuts part way into the
first circle. This b repeated
until <the whole surface b
covered with the part circles.
The effect b pleasing and
the surface b not easily
marked by light scratches
that would show plainly on
a highly finished piece of
steel. It is an economical
method of producing a fairly ^worh ^

u . u u
n 1 n

•

./ly

good finish.

Ease of Cleaning Bear- ^

ing Surfaces. A jig should be ^* ^" Se.t.ng Surface, for DnlUt.

constructed so that it can be easily cleaned. Chips or dirt between
the piece of work and the seating surface, or between the work and the
stops, or locating points, throw the work out of true, and, as a result,
the holes will be at a wrong angle to the working surface, or they will
be improperly located. Either condition would make the pieces unfit
for use on most work; consequently, bearing surfaces should be cut
away, wherever possible, leaving several small seating surfaces, rather
than one large one. In A, Fig. 255, b shown a piece of work resting
on its entire seating surface, while B shows a surface cut away to
leave six bearing points. If the seating surface is to be cut away,
the raised portions should be so located that the article cannot be
sprung by the action of the cutting tools or from any pressure that
may be applied by any fastening device^ otherwise the work will be

166

TOOL-MAKING

thrown out of true as badiy as though chips were lodged between
the work and the seating.

It is advisable, whenever possible, to divide a long locating
bearing into several short surfaces, and thus to decrease the c^nce
of holes being inaccurately located. When making jigs for pieces
that are likely to have burrs at any given point, it b well to cut a
depression in the seating or locating surfaces for the -burr, thu& pre-
venting the work being incorrectly located.

Seating surfaces should be made smooth so that chips and dirt
will not stick to them; but they should not be polished or finished, as
this would involve unnecessary cost and might throw the surface
out of true.

Avoidance of Clumsy Design. A jig must be handled by the work-
man, and a clumsy jig is difficult to manage. Sharp comers should
be avoided wherever possible, and all handles or similar devices
should fit the hand; if th&y do not, the amount of work done will not
be the maximum, as the operator cannot do so much work with a
jig which tires the hand and wrist.

As already stated, the accuracy with which a jig should be
constructed depends entirely on the nature of the work to be done;
yet it should be borne in mind that any inaccuracy must of necessity
be duplicated in the work.

Sunple Slab Jig. A few designs of jigs will now be considered,
to show the general requirements and the methods of construction.

The slab jig. Fig. 256,
is the simplest form in use;
it consists of a piece of fiat
stock of suitable thickness
and of the same general out-
line as the piece to be drilled.
The work may be clamped to
the jig by means of U-clamps,
or parallel-jaw clamps. If the jig is made of machine steel« the
walls of the holes should be casehardened by heating the jig red
hot and sprinkling powdered cyanide of potassium around the hole,
reheating it in the fire, and plunging it into water; it should be
worked back and forth in the bath so that the water will circalate
through the holes.

Fig. 25A. Slab Jig

TOOL-MAKINC

167

Slab Jfg with Bushing Holes. While the simple slab jig answers
very well where but a few pieces are to be drilled, it is not suitable
for permanent equipment on
account of the wear of the
holes. To overcome this, the
holes may be made suffi-
ciently large to receive hard-
ened bushings having holes
the size of the drill to be
used. Fig. 257 shows this irsmjamH Maw ^^^

Fif. 267 Jic Providad with Bushings

construction.

Stops and Holders for

■ftn"

> ii I

Work. When holes are to be drilled at certain distances from one
or more edges, it is necessary to- have stops against which the work
may rest. These stops may
be pins, a shoulder, or a rib.

If the outline of the
work has been finished by
any process that insures uni-
form lengths and widths,
such as milling, punching, or
profiling, the locating points
may be placed on all sides
of the piece in which pina
are used as stops, or locating
points, as shown in Fig. 258.
It is necessary to flatten the pins on the sides that come in contact
with the work, to prevent rapid wear.

When a jig is to be
used constantly, it is
advisable to have a
shoulder or a rib rather
than pins, for the work
to rest against,, as the
former will not wear so
rapidly as pins. Fig. 259 shows the same form of jig as Pig. 258,
except that 'ribs are substituted for pins.

When there is no surety that the dimensions of the different

Fig. 258. Looating Pins on Jigs

Ftg. 2M: Locating Riba on Jigs

168

TOOL-MAKING

o n

Tig 260 Jig with Pin and Screw

pieces are exactly alike, it is advisable to locate the pieces in the jig

from certain portions. The work must be forced against the locating

points by means of a screw, cam, or wedge. With a screw, the work

may bc^ forced to position and
held there, even when the dimen-
sions of the piece vary consider-
ably. The cam is operated much
more quickly than the screw, and
holds the work firmly when the
size of the pieces varies but little.
For certain purposes, the wedge
is an admirable holding device,
but it is not generally used.
Fig. 260 shows a jig in which the
work is located from one side
and end, the work being forced
against the stops by means of

a screw; Fig. 261 represents the same jig having a cam instead

of a screw

Locating Holes for Bushings. Approximate Methods. When

making any of these styles of jigs, the holes to contain the

bushing may be located by sev-
eral methods.

First Method. If extremely
accurate work is not necessary,
a templet may be made, or a
model piece used having the holes
properly located, this piece is
placed in the jig and, by means
of drills, the holes are transferred
to the jig If the bushings are
to be used, the holes may be en-
larged by a counterbore having
a pilot which fits the drilled
hole, and a body of the desired
' size of the bushmg While this method is cheap, and good enough

for certain classes of work, it is not advisable to use it for a really

accurate job.

Fig Wl .lig wtth CaTn and PiD«

TOOL-MAKING

1S9

Second Method. Another inexpensive method which insures
fair results is to drill the holes as described above, and then to run a
drill or reamer, a trifle larger than the holes in the templet, through
the holes in the jig. Then
the templet is pieced in
portion, and, by means
of a counterbore having
a pilot which fits the
hole in the templet, the
jig is counterbored to
the templet. Fig. 262.
Better results will be
obtained if the ends of
the teeth of the coun-
terbore are made of the "'"'" "" ' *
shape shown in Fig. 263, especially if the drilled hole has run from
its proper location.

At times, it is advisable to use a hollow counterbore. Fig. 264.
A pin having one end a pressing fit in the hole in the model, and the
opposite end a nice runnbg fit in the hole in the counterbore, is pressed
into the model. The hollow counterbore, being guided by this pin,
cuts the bushing hole to size. The results obtained by this method
are about equal to those obtained by the previous one.

Third Method. A third method is used when the bushing holes
must be located by measurement, or when there is no templet or
mode! piece. By means of a surface gage, having the point of the
needle set at the proper height from a scale attached to an angle iron.
Fig. 265, a dimension Ibe is scratched on the surface which has been
colored with blue vitriol. The needle is first set to the height of the

locating rib. The sc^e attached to the angle iron is adjusted so
that the needle is at the exact height of one of the inch lines, if possible;
if not, at one of the half-inch or quarter-inch lines. The needle can

170 TOOL-MAKINO

then be raised to locate the ceoter of the Gnt hole, and a line scratched
while tiie jig ts on edge. The centers of the other holes are nOw lud
m on this plane, after vhich the jig is turned one^iuarter of the way
around to locate tJie hole
from the other measurements :
where the lines Intersect, the
surface of the jig should be
prickpunched. Forthiswork,
the center punch Inade Tor
centering work to be turned
in the lathe, must not be used,
but rather the prickpunch,
which should be much lighter
than the ordinary center
punch. Fig. 266. In order
that the point may be per-
fectly round, the point of the
'''iirtliM'^^^^pJillUJ'sShd ^''iTST'' prickpunch should be ground
in some form of grinder, in
which it can be held and revolved. If this is not done, it will
be impossible to get the point of the center indicator to run true
ii4wn attMDpting to true the jig on the faceplate of the lathe.

While the method just described might be properly classed as
ui ftpproximate measureinent, an experienced workman can locate
tfae bu^ungs within a small limit of variation. More accurate work

TOOL-MAKING

171

will result if the height gage b used in laying off the dimension
lines. The bottom surface of the extension is set to the height of the
locating rib, as shown in Fig. 267; then, by means of the vernier, it

Pig. 26f(. Typical Prickpunch and Center Punch

can be raised to the exact height of the dimension desired, and the
line scribed by means of the point of the extension. This method,
alt*hough it insures greater accuracy in laying off dimension lines,

Fig. 267. Use of Vernier Height Gage for Accurate Ix>cation of Jig

and is sufficiently exact for most work, is open to the objection that
the tool-maker may change the location of centers somewhat when
prickpunching.

172

TOOL-MAKING

Ex€ut Method, When preciBe measurements are desired, many
tool-makera determine the location of bushing holes by means of
hardened discs or buttons. A very common size, Fig. 268, is } inch
in diameter, A >nc*^ thick, and has a J-inch hole. WhDe it is not

essential that the diameter be any particular
size, it must be some fraction divisible by
two without a remainder, as one-half the
size of the disc is considered in all computa-
tions. If the disc is .500 inch in diameter,
.250 inch is the decimal to be considered; but
if the disc were A (.5625) inch in diameter,
it would be necessary to consider the deci-
mal .28125 in all computations. In locating the disc, most of
the n^asurements are made with the vernier caliper, and as the
tool* not graduated to read closer than .001. inch, it would be
impossible to take into account the fractions of a thousandth of an
inch; consequently, discs. .500 inch in diameter are generally used.
The locations of the different holes are laid off by means of the surface
gage, the needle being set to the scale fastened to an angle iron, as
already described. The holes are drilled and tapped for screws
somewhat smaller than the holes in the discs, and the discs are
attached to the jig by means of screws. As the screws do not fill

Plf. 268. Hardened Disca or
Buttoas

Pis. 269. Jigs with Discs Located from Slope

the holes in the discs, they may be moved until properly located
Fig. 269 shows a jig having the discs located in relation to the stops.
• After properly locating a disc at each point where a bushing b
desired, the jig is fastened to the faceplate of the lathe. The jig

TOOL-MAKING 173

most be so lorated on the faceplate th&t one of the discs will run
peifeclly true. This can be determined by a teat indicator operating
on the outside of a butttm, as shown in Fig. 270. After the disc has
been so locatedj it can be removed and the hole boi^ to the required
size. The jig can now be moved to bring another disc to the proper
location, after which it is removed and the hole bored; this operation
is repeated until all the bushing holes are bored.

Borliv Bushinf Holes on Milling Machine. In order accu-
rately to locate and machine drill jig bushing holes on a unviersal

millbg machine, it is necessary to use a machine provided with a
corrected screw and index dial for each of the graduated movements,
With such a machine and proper tools, it is possible for the skilful
workman to produce a drill jig that is correct within reasonably nar-
row limits. If many jigs are made and corrected screws are furnished,
it b not advisable to use the machine for heavy milling. Many
shops provided with such a machine do not use it for anything
but jig work, and laying out models and similar pieces.

The skilful workman always looks the drawing of the jig over
carefully, and selects a suitable working point from which to start.
This working point should be one from which it will be possible to

174

TOOL-MAKING

move in the directions necessary in locating other working points,
so that no backlash will occur in the adjusting screws. In other
words, we must commence at one end and move constantly ahead.

It may be necessary to raise
and lower the knee of the
machine to obtain vertical
adjustments, but we should,
when lowering, rather run the
knee below the desired point
than raise it up to it. In this
way we avoid error.

Angle Iron and Indicator.
If the jig can be fastened to
an angle iron, as shown in
Fig. 271, the face* of the angle
iron against which the work
is clamped should be set ex-
actly parallel to the travel of
the table of the machine. A
Bath indicator, or an indicator
of the design shown in Fig. 272,
may be clamped to an arbor
in the spindle of the machine, or one may be held in a chuck screwpd
on the nosic of the spindle, or in a chuck with a shank, fitting the
hole in the spmdle. Fig. 273. . By running the table of tlie machine

Fig. 271

Drill y\% Fa<tene<I to Angle Iron
for DrilliDf

.n<. 272.' Indicator for Ix>eating Buskiog Bolcf

back and forth with the contact point of the indicator against the face
of the angle iron, and moving the iron until there is no change in posi-
tion of the indicator needle, the angle iron may be correctly located.

TOOL-MAKING

175

SUne and Shot. A button is attached to the jig &t exactly the

location o( the first bushing hole. The jig is fastened to the angle
iron, and the proper adjustments made so that the sleeve £, Fig. 271,
wiU slide over the button, making sure that the table of the machine

Fit ^^ InthHtdT wiih Shftnk Fittinc RdI* Fu. 374. :EI«trii; OriAdnr l9r GriBdlu

In S|ii»Ui Tor Lontict BiuUd) (Mh Stud to SlH

is moving in the direction necessary to get the other adjustments.
In order to insure accuracy, it is necessary to use a sleeve having a
hole nhich is a nice sliding fit over the button. In order that the
sleeve may be exactly true, it is necessary to make the outer end of
the stud somewhat large, then turn it after it is placed in the collet,
the cutting tool being held in the milling machine vise. The stud
revolving with the spindle may be turned by bringing it in. contact
with the cutting toiil; the tool feed may be obtained by moving the
saddle. As the modern milling machine is provided with automatic

saddle feed, a very smooth cut will be obtained. Excellent results
follow if an electrically driven griiider.'Fig. 274, is fastened to the
table of the machine, and the stud ground to size- It b obvious that
the«leeve must be a nice fit on the stud.

176

TOOL-MAKINQ

DriUirig and Boring Holet, When the jig has been properiy
located, the stud b removed from the collet, the button taken from the
jig, a drill placed in the collet, and a hole drilled through the jig.
A boring tool should now be placed in the collet, and the bushing
hole bored to size. Various forms of boring tools are used for work
of this kind. A very satisfactory form is shown in Fig. 275, the
cutter being securely held by the set screw shown. When using this
form of boring tool, the cutter may be moved out any desired amount,
the distance being measured by the micrometer.

After boring the first hole, the table may be moved to bring the
next location into position for drilling and boring. Suppose, for
example, it is necessary to drill and bore bushing holes in the piece
shown in Fig. 276. A button is fastened to the surface at A ; after

the location has been

^ determined as previously
described, the button is
removed, and the hole
drilled and bored to de-
sired size; the carriage
is then moved 1.1875
inches, and the hole is
drilled and bored. The
knee is then raised 1 .0625
inches; the hole B is
drilled and bored; the carriage is again moved 1.250 inches, and the
hole C drilled and bored. The jig is then removed from the angle
iron, the bushings made, hardened, ground, and forced to place.

Making Jig to Model. In the case of a jig that is to be made to
a model, the model 'is exposed if the jig is provided with a leaf, which
may be thrown back. Now, by means of a plug inserted in one of
the holes, the jig can be accurately located until the sleeve on the stud
rings over the plug. The plug can be made with one end a nice fit
in the hole in the model, and the other end a nice fit in the sleeve.
When the jig is accurately located, the leaf may be closed, and the
hole drilled and bored as in the previous example.

Vertical Attachment for Boring Holes, The vertical attachment
furnished with the modem universal milling machine provides a
means for boring bushing holes in the jigs that for some reason are

Fie. 276. Locatioa of Bushint Hole* in Drill Jig

TOOL-MAKING IH

fonnd difficult to attach to an angle iron. The jig is daxqied to th«
taUe tJ the machine and die buttons located by means of a test
■ndicator, lometiiiMs called a meep indiaiior. After each button
has been located accursttdy, it is. removed and the hole drilled and

Borinn Hole* at Rifht AngUi to Each Other. In the case of jigs
havingbushingholeson the sides at light angles to each other, the jig
can be strapped to the table of the milting machine, and the holes' in
the vertical portion produce^ by tools held b the regular horizontal
spindle, while those in the horizontal surface can be produced by
tools in the vertical spindle.
This insures th«r being
exactly at right angles to
each other.

Borms HoUi at Other
thm Rijht Attftee. At times
jiga are made with bushing
boles at other than a 90-
degne angle to each other.
In nieh cases, the jig can be
attached to tbe table of the
machine as previously de- ''•7^
scribed, and the horizontal,
or vertical botes, as the case
may be, produced by tools in the horizontal, or vertical spindle;
tlie holes at an angle can I>e machined by tipping the vertical spindle
to the proper angle, locating the position of the h<de» by buttons
and sweep indicator, then drilling and boring them at the desired
angle with toots held b the'vertical spindle, provided such spbdie
is equipped with a device for feeding it at the given an^e.

Fig. 277 shows a milling machine having an bterior spindle,
that can be fed at the angle to which the vertical spindle is set

Method of Loeaiinf) Jig on Angle Iron. A very satisfactory and
convenient method of locating a jig oa an angle iron for use on a
milling machine in boring bushing holes consists in boltbg two good
parallels to the face of the angle iron, as shown in Fig. 2^.

The parallels may be set at right angles to each other by means
<d an accurate tiy square, exactness of position being attained by

178

TOOL-MAKING

the use of draw papers as shown at aa. The use of draw papers is
to be recommended for many classes of work where extreme accunuy
is essential. It is customary to use tissue paper for this purpose and

Fig. 278. Atlachment for Drilling Holes at Angl«f

to place a strip of the paper at either end of the square blade, as shown;
when the blade re^ts against the work, the accuracy of the set may be

determined by attempting to draw
the papers. If one is securely held
by contact with the square blade
and the other is not held, it is
apparent that the pieces are not
correctly located. If both pieces
of paper are firmly held by con-
tact with the square blade when
the beam is securely set against
the other piece, it is apparent that
the two pieces ar^ exactly at right
angles with each other.

The work should now be fas-
tened to the angle iron, with the working edges against the parallels,
as shown in Fig. 279, and the machine adjusted until the buttofi
that marks the location of the first hole to be machined is properly

h--?

r ■

1 o

] ■

Fig. 279. layout Showing ParaltoU.

l^yi
Ited

Bolted to Angle Iron

TOOL-MAKING

179

located. After the first hole has been drilled and bored to size, the
jig should be moved to bring the location for the second hole into
proper position by placing a thick-
ness block of the proper size
between the end parallel and the
jig shown in Fig. 280. If no
thickness block of the right dimen-
sion is available, the jig may be
located by means of a plug gage;
or a vernier caliper or a piece of
wire may be filed to the desired
length and used in setting. This
assumes, of course, that this hole
is the same distance as the first
from the bottom edge; if it is on a *''' '^- *''■"'* ''*^ ^""« ''*"' "°''
different plane, the jig must be blocked up from the p»brallel by
means of thickness blocks to bring it to the proper height, as shown in
Fig. 281. By thts method it is not
necessary to use more than one
button or to locate the position of
more than the first hole. The
table and the knee of the machine,
being securely locked in position
cannot move, and as the jig is
moved the exact distance that
should separate the holes each time,
the holes may be accurately located
within a fraction of a thousandth
of an inch, which is near enough
for most jobs.

Fig. 281. Another Method for Locating
Second Hole

■\j

i_r

Fig. 282. Cant-Iron Jig with Solid Cast Legs

Jigs with Legs. When jigs are made for permanent equipment,
or if they are to be used constantly, it is well to provide some means
of elevating them from the drill-press table to avoid inaccurate work

180

TOOL-MAKING

occasioned by chips. If the jig is of cast iron, the legs are somet mes
cast solid with the jig, as shown in Fig. 282. In order that the jig
handle may be grasped in a manner that will nut tire the wrist or

Fig. 283. Jig with Cowr

hand, and in order to give sufficient room between the handle and the
table of the drill press so that the fingers may not be cut by chips, the
legs should be made of a length that will raise the handle about 1}

-^/r

Fig. 284. Covered Jig Showing Space between Work Mid Leaf

inches above the table. As cast-iron legs of this length would be too
weak, it is customary to make the legs of tool steel, hardening the

ends that come in contact with

the drill-press table.

Jig for Rapid Work, While
the form of jig shown in Fig. 256
would give satisfaction on cer-
tain classes of work, the process
of putting the work into the jig
and taking it out would be very
slow, as it would be necessary to
clamp the work securely to resist
the pressure of the cutting tools.
In order that work may be handled rapidly during these opera-
tions, jigs are designed so that the work will rest on the base of the

Fig. 285. Jig for' Drilling Holes from
Both Sidee

TOOL-MAKING

181

jig as shown in Fig. 283. A leaf or cover 6ontaining the bushings can
be raised when putting the work in place and taking it out.

When the pieces to be drilled are of a uniform thickness, the
leaf may be made to rest on the piece; but should they vary in thick-
ness, the leaf would not be parallel to the base, and, consequently,
the hole in the bushing would not be at right angles to the piece to
be drilled. For this reason a little space is left between the top of
the piece to be drilled and the bottom of the leaf, as shown in Fig. 284 ;

Fif(. 28A. Jig with L^gK on Both Sides

a steady pin having a shoulder is located at the handle end of the jig.
The upper end of the pin may project into a hole in the leaf, as shown,
thus relieving any strain on the joint of the jig occasioned by the
action of the cutting tools.

Jig for Holes on Opposite Sides. When holes are to be drilled
from opposite sides of a piece of work, as shown in Fig. 285, a jig may
be constructed having legs on both upper and lower sides, but both
sets of legs should be solid with the base, as shown in Fig. 286. /

182 TOOL-MAKING

If the two end holes in Fig. 285 are or the same size, and it is
necessary to use a drill presa huiing hut two spiiulles, the legs on each
Ride must be of a length that will make it possible to set tlie stops
9u that the drill will cut the lequired depth on each side. IF a drill
press having three or more s|Hndles is to be used, the jig le^ rosy be
of a convenient length, as two drills of the same diameter can be used
in two different spindles, each one to drill the required depth when the

Corwlnidion nf Legn. Drill jig legs are generally made ot tool
steel and are screwed into the base of the jig. The thread on the
legs should be a good fit in the base. After having been screwed

into (dace, the ends oF the legs should he machined to length by milling
or planing; the legs can then be removed, and the ends that come
in contact with the drill-press table hardened. The legs should now
be polished, if that is allowed, and screwed into place. The ends
are then ground to such a length that the surface where the work
is seated will he of the correct height above the drill-press table.

Grinding the ends of the legs can best be done in a surface
grinder, or some form of universal grinder designed tor surface grind-
ing. After grinding, the ends of the legs should he lapped to remove
any irregularity that may result from grinding. A very good lap may
be made from a flat pUte or block of cast iron. The surface to be
used should be planed flat and smooth, then a series of grooves cut

TOOL-MAKING

183

to form squares, as shown in Fig. 287. These grooves should be cut
with a V-shaped tool and should be } inch apart, and g'c inch to
3V iuch deep. The grooves catch the emery and feed it to the work
being lapped. If the pressure is not equal » one leg may be cut shorter
than the other, or may be lapped out of true, causing the jig to rock.

Jigs with Cored Holes. As large jigs are usually made from
cast iron and as it is advisable, when the holes are large, to core them,
it is necessary, in order to lay off the location of the center of the
hole, to insert a piece of steel or brass a. Fig. 288, in the hole and then
to determine the desired point on the inserted metal.*

Where the button method is to be used, a button of a size some-
what larger than the cored hole is required; and this, bolted against
the face of the boss in the proper location, enables the workman

Fig. 288. Locating Center of Cored Hole
in Jig

Fig. 289. Use of Buttons in Using Bore-
Bar for Bu.shing Holes in Jig

properly to locate the jig on the faceplate of the lathe. If the jig is
too large to swing in the lathe, it may be fastened to the table of the
boring mill and trued by means of an indicator held in the cutter
head of the machine; or the jig may be attached to the milling
machine table, and the bushing hole bored, as described on previous
pages.

When properly located, the piece of brass and steel may be
knocked out of the hole, or the button may be removed and the hole
bored to desired size. Many tool-makers always drill or file the walls
of a cored hole to remove all hard scale, as there is always more or
less danger of knocking a piece of work out of true when cutting ,
through cast-iron scale. When the scale is removed before machin-
ing, there is little likelihood of moving the work if it is securely
clamped to the machine, and the workman is reasonably careful.

184 TOOL-MAKING

In work or this character, the workman is not expected to take
such heavy cuts as would be taken on manufactured articles which
are securely held in specially designed linldfusts; and he should lie
particularly careful when taking cuts where there is more stock to
be removed on one side than on the other, as the unequal strain is
especially likely to throw work out of true.

The warning given elsewhere should be repeated: A'^tvr renin
a bushing hole; always machine to si^e with an inside turning ton],
or with a boring bar where such a tool can be used.

Under certain conditions, especially where a iHirinj; bar is to be
used, either in the boring machine or in a lathe where the work is to
be fastened to the carriage and the boring bar supported on the
centers of the lathe, buttons nre used which
hai'e several holes passing through them, as
shown in Fig. 2S9. These holes are somewhat
larger than the cap screws which attach tlie
button to the fa<;e of the jig. The button has a
hole through the center A oi" i '"ch larger than
the desired hole in the jig. It is accurately
located on the face of the jig, which is then
placed on the machine and fastened in posi-
tion. To locate the j ig properly, the boring bar
»!, 190 Rorinc Cuuw '* passed through the cored hole andplaced in
rin^a.S^iS^ position; then by fastening an indicator to the
lathe spindle and rotating the latter, the but-
ton can be set so as to be equidistant at all points from tlie bar.
This method will compensate tor any eccentricity in the boring bar.
The advantage of thb form of button is that it can be left in
position on the jig while the hole is being bored; and when the hole
is finished, a plug may be inserted, and the hole tested for accuracy
of location.

At times, it is desirable to use the method described above
when tlie hole passes through hut one side of the jig and it would nut
be possible to carry it through the other side. In such a case, a boring
tool which screws on the nose of the spindle or fits into the spindle
hole may be used. Such a cutter is shown in Fig. 290.

TOOLMAKING

PART III

STANDARD TOOLS

DRILL JIQS

Fastening; Devices. Various, devices are used to fasten the leaf
of a jig to hold the work in place, or to clamp the leaf in position.
The forms used depend upon the class of work being operated on.

If the leaf must be fa&tened solidly, and the amount of time
consumed is not of great importance, some form of terew damp
may be used; but if the work must be handled rapidly, the damping
device is generally operated by some form of cam. However, a screw

Fig. 991. Screw Cl«inp for Jifl

clamp may be designed to work quite rapidly, and such a one is
illustrated in Fig. 291. This screw clamp consists of a screw with a
hole drilled through it to receive a pin that is used as a lever to oper-
ate the screw. The screw is necked ^ inch deep, the necking being
i inch wide; a flat washer is attached to the leaf of the jig by a small
screw, as shown. A slot the width of the screw is cut in this washer
to allow it to slide back and forth, and in the end of the washer is
a slot the width of the bottom of the necking in the screw. The
other end of the washer is turned up, as shown, to furnish a means
of pushing b&ck and forth. When the jig leaf is closed, the washer
is pushed forward and the ends engage in the slot in the screw.
One turn of the screw binds it very tightly. When the screw is
given one turn to loosen it, the washer may be pushed back and the
jig leaf raised.

186

TOOL-MAKING

Where, it is not necessary to use miidi power, but extreme
rapidity of action is desired^ a hinged earn Ueer of the design shown
in Fig. 292 may be used. The cam lever is pivoted to the base of
the jig by means of a pin as shown. The lever passes into a slot

Fi«. 202. Hinged Cain Lever for Jig

in the leaf, and the bearing surfaces on the under part of the head
come in contact with the inclined surfaces at the end of the leaf.
Bushings. Bushings of hardened tool steel are made as a
permanent guide for the cutting tools. The hole in the bushing
is made to fit the cutting tool that is to be guided. There are
various forms of bushings; the plain straight form, Fig. 293, is some-
times used, but is objectionable because it may be pushed into
the jig if the cutting tool is too large to pass through the hole. To
overcome this tendency, bushings are sometimes made tapering
on the outside,, a& shown in Fig. 294; but as this is an expensive
form, and as it is an extremely difficult operation to bore the bushing
hole in the jig, it is not generally used for permanent bushings.

The most common
form of bushing is
straight, with an enlarged
portion or head. When
no allowance is made for
grinding on the outside,
the bushing is usually
made in the form shown
in Fig. 295. If the shoulder under the head is square, it is likely to
crack at the sharp comer, or the head may be broken off when
being forced into position. In order to avoid these diQiculties,
a fillet ifi left under the head, as shown in Fig. 296. '

Fig. 293. Biuhing with

Straight Out

ing K
ttiae

Fig. 294. Bushing with
T«|i»ring Outside

TOOL-MAKING

187

Grinding. When it is essential that the location of the drilled
hole or portion of the piece being machined in the jig be exacts the
tool must fit well in the bushing; and as the size and shape of the bush-
ing are likely to change in the hardening, it is advisable to leave
enough stock to grind to size, both inside and out. It is essential
that the outside of the bushing be exactly concentric with the inside.
After the hole is ground and lapped to size, the bushing may be placed
on a mandrel which runs true, and the outside ground to size. When
machining a bushing which is to be ground on the outside, it is
necessary to neck in, under the head, as shown in Fig. 297, in-order
that the emery wheel may pass entirely over the*part being ground
and insure a straight surface. The under side of the head which

Fig. 295. Common
Bushing

Fig. 296. Bushing with
Fillet under Head

Fig. 297 Necked
Bushing

rests on the upper surface of the jig should be ground so that it may
be true with the surface of the jig.

When grinding a bushing, a mandrel should be used which is
straight or of very slight taper and has beeq tested for trueness. If
the taper is considerable one end of the hole in the bushing will not
fit, and the outside of the bushing will not be concentric with the
hole. Consequently, no matter how careful the- tool-maker may
be in laying out his work and in boring the holes for the bushings,
the jig will not be accurate. »

Size of Bushings. The outside diameter of a bushing is often
determined by the design of the jig; for instance, two holes are often
located so near each other that it is impossible to make the bushings
much larger than the holes through them. Whenever possible,
the outside diameter should be made enough larger than the hole
to leave a reasonably thick wall. A bushing with thin walls is likely
to close in when being pressed to its seating; also, if a cutting tool
binds in a bushing with thin walls, the bushing turns in the jig.

ISS TOOL-MAKINO

RemoiabU Btuhingi. It is sometimes lidvisable to perfonn
two or more operations in the same jig. After e. hole has been
drilled, it may be that it will be considered good practice to counter-
bore or tap it, or, possibly, it may be better to do the three operations
white the work a seated in the jig. In such cases the bushing having
a hole the size of the drill must be removed, and one inserted that
has a hole fitting the to<^ to be used.

A very simple way of milking a removable bushing consists
in boring the hole in the jig large enough to receive a hardened
bushing with a, hole the ^ze of the outside of the bushing to be used.
If the hole in the large stationary bushing and the outside surface
of the removable bushing are la^^ied smoothly after grinding, they

Fl*. Jn. KBmnnUB BubIpdc.
Thrudi Run Ed(it> Lcititb

may be used for a long period before wearing enough to affect appr^
ciably thebcation.

Tapered removable bushings are sometimes used, but on
account of the expense of producing them, and the fact that chips
and dirt readily throw them out of their true locations, they ai;:
not very common and their use is not advised.

Fig. 20S sKows a form of removable hushing tiireaded on the
outside to fit a threaded hole in the jigi If the thread on the outside
of the bushing runs the entire length, P^ig. 299, the process of screwing
it in and out of the jig is necessarily very slow; consequently it is
advisable to have but a few threads. The balance of the length
may be made to fit a bearing in the jig. If it is advisable to thread
the entire length, the hole should be ground true with the thread
to prevent change of shape in hardening. As it is not well to attempt
to grind between the lands of the thread with the facilities in the
ordinary machine shop, it is necessary to grind the hole true with
the thread. This can be done satisfactorily by placing a piece of

TOOL-MAKING

189

stock in a chuck on the lathe having a grinding attachment. After
drilling and boring the hole to tapping size, the thread should be
chased so that the bushing is a good fit in the hole. It can then be
screwed in, and the hole ground to size.

Box Jig. If the piece of work is of a shape that makes it neces-
sary to operate on all sides, and the outline prevents the use of a
clamp jig of the form shown, a box jig must be used. * A box jig
is made in the form of a box, the piece being located in the jig by
means of stops or locating points which differ according to the nature
of the work. It is often advisable to design this form of jig so

Fie. 300. Special Piec« to Ce Drilled

that all holes in the work can be drilled at one setting; that is, if
there are twenty holes in the piece, it is designed to allow the drilling
of them all while the piece is in the jig. For other work it is advis-
able to make two or more jigs to drill the holes; this is the case
when some part of the piece is to be machined after one or more holes
are drilled, but before drilling the others.

In Fig. 300 a piece of work is shown (about three-eighths size);
through the piece it was necessary to drill three Uinch holes as shown
&t Af A. and B. As the holes A A must be an exact distance from
B\ it was found by experience that much better results could
be obtained if the hole marked B was drilled and reamed in a ji^,

190

TOOL-MAKING

the piece taken out of the jig, and the portions marked CC milled
in exact relation to the hole B and as nearly as possible at right
angles with the side of the casting marked D. After the
portions CC had been milled, the piece was placed in another jig,
locating it by the hole B and the surfaces CCi the holes A A were,
then drilled and reamed. In order to drill the hole B, the jig shown
in Fig. 301 was used. The piece was placed in the jig with the
rounded surface ^,.Fig. 300, resting in two V-blocks, A^ Fig. 301.

Fig. 301. Jig for Work Shown in Preceding Figure

It was located by means of the fixed stop screw B, and forced against
-4 by the screw; it was held in position by the screw £, which was
located in the strap 2), this strap being removed when putting a
piece of work in the jig or taking it out. As it was necessary to
have the hole straight and true with the locating points, it was reamed
with a single-lip reamer having a pilot, Fig. 302: The hole was
drilled somewhat smaller than finish size (^ inch), and the reamer
was entered in the hole, the pilot fitting the bushing (?. While

TOOL-MAKING

191

the body of the reamer fits the bushing F, lis previously explained,
the single-lip reamer acts on the same principles as a boring tod
used in the engine lathe, the result being a hole straight and true.

Fig. 302. Single-Lip Reamer with Pilot

As it was necessary to have the hole in the upper bushing of the
size of the body of the reamer, and as a drill ih inch smaller than
this size must be used, it was advisable, in order properly to start
the drill, to use a transfer drill, shown in Fig. 303, the cutting por-
tion A being the size of the drill to be used in making the hole,
while B fitted the hole in the bushing. By means of this drill,
a hole the size of the drill to be used was started in the casting,
perfectly true with the hole in the bushing, yet somewhat smaller.
When the hole had been drilled to a depth of ^ or J inch, the trans-
fer drill was removed, and a twist drill of the proper size used to
finish. When the piece of work was taken from the jig, the portions
marked CC^ Fig. 300, were milled as explained. The piece was then
placed in another jig, and a pin fitting the reamed hole passed through
the locating bushings and through the hole; by this means the other
two holes could be accurately located and drilled. The second
jig so closely resembles the first that it is unnecessary to illustrate it.
Jig for Holes around Circular Shaped Pieces. At times, it is
essential to design a drill jig for drilling holes, either equally or

Fig. 303. Tran-sfcr Drill

unequally spaced, around a circular shaped piece of work, such as
the six equidistantly spaced holes around the circumference shown
in Fig. 304. These holes are all radial; but a jig of this type

192

TOOL-MAKING

may be designed to drill holes that are not radial, or it may be
designed to drill a number that are radial and others that are not

Fig. ^)34. Drilliag around Circular

radial by locating the bushings to produce the holes in the desired
locations.

Fig. 305 shows a jig with but one bushing designed to drill
the six holes in the piece shown in Fig. 304. The spacing of the
holes is determined by the index plate i4, while the work is held
on the stud B. As th^ holes, must be accurately located with the
keyway in the piece, the stud in the jig is provided with a key to
fit the keyway. The dial plate being keyed to the stud jB, the holes

Fig. 305. Jig with One Bushing to Drill Six Holes

drilled in any number of pieces will all exactly correspond with the
location of the keyway and with the holes in all of the other pieces*

TOOL-MAKING 193

While the dial shown on the jig in Fig. 305 is designed to drill
six evenly spaced holes, the holes in the edge to receive the locating
pin might have been cut in any desired number and have been
spaced to produce holes of ah uneven distance apart.

If large drills are to be used in connection with the jig, it. is
advisable to provide some method of binding the stud to prevent
any strain on dial and pin for such a strain would tend to render
the jig inaccurate after it had been used for a time.

In the case of the jig shown, the portion of the body of the jig
that provides a bearing for the stud is split and supplied . with a
binding screw and 'lever. The stud should be securely locked in
position each time the piece is turned to locate a hole to be drilled.

If holes are to be drilled at different distances from the shoulder,
two or more bushings may be provided. If the holes are all of one
size, such an arrangement of bushings may lead to error unless the
locating hole on the dial is so stamped that the operator can
by looking at it as the pin enters, see which bushing the drill
should enter.

Thb form of jig is capable of almost endless variation of design,
and can be made to accommodate not only pieces that are round in
form, but those of almost any form where holes are to be drilled
around the outer surface. In ^ome shops the work is of such form
and the holes are so arranged that many jigs of different design
arc not necessary, but all of above types are used.

PUNCH AND DIE WORK

Dies. A die used for punching a blank from a sheet of metal
is termed a blanking die, and is generally considered as belonging
to one of three classes: plain (or simple) die, gang die, or com-
pound die.

A set of blapking dies consists of a male die, or punch, and a
female die, or die block. The die block is that part of the die which
has a hole of the same outline as the desired blank; the male die, or
punch, is of a shape that fits the impression or hole of the die
block.

When punching work on a punching press, the stock is placed
on the die and the punch forced through it into the die; this drives
a piece of stock of the same outline as the hole down into the die

194 TOOL-MAKING

block. Ab the punch is forced through, the metal in the sheet has
a tendency to close on tlie punch and to be raised by it. In order
to prevent tlijs, the die blwk is provided with a tlripper plate, or
itrlpper, which is fastened to the die, or to a shoe holding the die,
at a height that allows the metal to be punched to pass freely between
it and the die. The stripper must be strong enough to force the
stock from the punch without springing, especially if the punch is
slender »nd the stock thick, for if it did not, the punch would be
sprung or broken.

In order to guide the stock over the die and leave the proper
MDOunt of margb or scrap at the edge of the sheet, a giiiile is fur-
nished. The guide is
usually made of stock
sufficiently thick to bring
the stripper the proper
height above the face of
the die. A gage pin, or
ttop, is usually provided,
GO located that the proper
amount of scrap is left.
Boder Pla (e Punches.
Punches for use on boiler
plate and similar material
arc made with a locating
point as shown at B,
Fig. 306. This point
enters a prickpunchcd
Fif. MM. '^£jl;,','^„^?;j'^"' siwirini mark, and so locates the

sheet for punching. The
workman laja olT and prickpunches the sheet where each hole
should be; the sheet is then taken to the punch press, and each
hole is punched as laid olT.

Punches fur Large Ilolea. In Fig. 306, A is the form gencrallj'
used for punching large holes, or for heavy material. If the face oF
the die is made flat, it is necessary to shear the punch. The die is
made round in form, as shown, and b held in the bolster by means
of a round-end set screw which enters a cut on the side of the die
near the bottom.

TOOL-MAKING 195

In Fig. 307, -4 is the die block, C tlie Imie through tlie die block
of the shape of the piece to be puntbtd, C the stripper, D t'le guide,
and E the gage pin or stop.

Die Holders. Dies are held in position on the punching press
l>ed hy various methods.'the most coDimon of w|iich are the forms

cn""

of holdfast shown in Figs. 30S and 309. These die holders an
known by various names, such as cbair, bolster, and chuck. Large
dies are clamped to the bed of the press.

Dies are usually beveled on the edges that come in contact with
the die holder, to prevent their rising from the seat. The an^e
giten to the edges varies
according to the ideas of
the designer. An angle
of 10 degrees from the
vertical gives satisfac-
tion, although some me-
chanics insist on an
angle of 15 degrees or
even 20 degrees. r., sos. Fo-m »( iioidi^.

Fig. 310 shows a die holder with a die whose edges are at an
angle of 10 degrees; the die b held in place by set screws. It is
generally considered advisable to place a gib, or shim, between
the set screws and die as shown. Sometimes the gib is omitted,
and then the set screws bear directly on the edge of the die. Some

196

TOOL-MAKING

Fig. 309. Form of Holdfast

tool-makers prefer a die holder without set screws, and hold the
die securely in place by the gib, which is made wedge-shaped and

is driven to place.

Fig. 311 shows a
method of holding dies
which allows them
to be easily set in posi-
tion when rigging up.
The die is placed on the
seating of the die* holder,
• and brought to the proper
position. The set screws
are then brought against the edge of the die, or against strips of
steel which are placed between them and the edges of the die.

Making Die* Preparation of Bar. When making several
dies of equal width and thickness, a good method is to plane the two
sides of a bar to remove the outer surface and to bevel the edges

to the required angle.
Pieces can then be cut
off to any length
wanted.

The upper surface
of the die bar may be
finished smooth by planing with a smoothing tool; it may be ground
in a surface grinder, or it may be finished with a file. It is necessary
to have the surface smooth in order to lay out the correct shape of
the hole; a roughly machined surface would allow neither distinct nor

correct work. The die must be
laid out in such a manner that
the stock may be readily fed
to it. If the grain of the stock ■
is a matter of importance, as
in making a tempered spring,
the worker must take care to see that the grain runs in the proper
direction

Marking and Drilling, The face, or upper surface, of the die
is covered with the blue vitriol solution, and the outline of the piece
to be punched is laid out. After the die has been carefully laid

Fic 310. Die in Holder

\wy////.

^gg^^ggga

Fig. 311. Easily Sot Die Holder

TOOL-MAKING

197

Fig. 312. Removal of Stock by Drillinit

out from a templet or drawing, all round corners should be drilled
with a drill of proper size; they are then reamed from the back side
of the die with a taper reamer to give the desired clearance, and
the balance of the stock is removed by drilling, as shown in Fig. 312.

The method of removing
the center, or core depends
on the custom practiced by
the individual die-maker.
One die-maker inay drill the
holes so that they break
nto one another, and for
him the best tool is a
straightway (straight fluted)
drill. Another will drill
small holes and use a counterbore to enlarge to size, the counterbored
holes breaking into each other. .Usually the holes are drilled
with at least lAr inch to ^ inch between them, and the intervening
stock is cut out with a flat-ended hand broach. Fig. 313. Generally
speaking, the last mentioned method is the safest and quickest.

Milling. After the center has been removed, the die may
be placed in a die milling machine or a die. sinking machine;
and by the use of a, milling cutter of the proper taper, the desired
angle of clearance can be given. The amount of clearance
varies with the nature of the w^ork to be done.

When a die is milled on a die milling machine of the form
shown in Fig. 314, the cutter spindle is underneath the die, the face
of which is uppermost; consequently the miiling^ cutter can be made
largest at the shanlc end of the cutting part, the required taper

Fic- 313. FIsi^End Hand Broach

being given as shown in Fig. 315. If the outline of the hole is
milled on a die sinking machine, it is necessary to use a cutter of
the shape shown in Fig. 316, in order that the face of the die having
the lines will be uppeimost.

198 TOOL-MAKING

Filing. After working the impression as near to ihape as
possible by milling, it can be finished by filing. In order to give
the die the proper clearance,
the walls should be gaged with
' a bevel gage of the form shown
in Fig. 8, Part I. As the clear-
I ancediiTers in various shops, and
on difTerent classes of Work,
no stated amoujit can be ^ven
for all cases; it varies from }
degree to 3 degrees. The latter
is excessive, and is seldom given
unless it is necessary that the
piece punched drop from the
die each time.

If the die is milled as just
described, it will be necessary
to work all comers to shape
with a file. If a universal mill-
ing machine having a slotting
attachment is used, the corners
can be properly shaped and the
necessary clearance given by
using suitably shaped cutting
ri». 314. Dit.\[,iUinM»chiM tools, and turning the fixture to ,

the proper angle.

Fig. 317 shows a slotting fixture attached to a universal milling
machine; while Fig. X\S shows a fixture known as a die shapcFt
which .3 also attached to a milling machine.

TOOL-MAKING 199

Die Filing Machine. In many shops the die filing machine,
shown in Fig. 319, U used for many of the operations of working to
shape dies, gages, templets, and various small parts. It b also
used in lapping dies, gages, and models, which have been hardened.
As the table of the machine can be set at an angle, dies can be filed
or lapped at the proper angle to give the desired,clearanee.

A saw may be used in place of the file, and the core of the die
sawed out, this is a very satisfactory way of cutting the core from
a small die having an irregularly shaped opening, whose outline

is such that the ordinary methods do not prove satisfactory, or are,.
extremely costly. For large work, an ordiiiarj" hack saw. blade
may be used,* holes being drilled at the corners of the openings.
For small work and where irregularly shaped openingsare to be pro-
duced, a narrow blade whose teeth have quite a little set b advisable.
For roughing out a die opening, a coarse file should be used,
the file being clamped at either end, and the work held against ■
it by means of the feed screw, while the die b guided by hand.
When taking finish cuts with small files, the file is usually held in the
lower clamp only. As the file clears on the return stroke, undue

200 TOOL-MAKINQ

WMr a avoided. The crank pin may be set at either end of the cruilc
Ann, as may be desired, so as to cause the file to cut at either the
up or down stroke.

Graduated table readinfp are furnished so th^t the table can be
set U> provide any angle of clearance. The surfaces produced by
this machine are flat, smj etpeciaUy adapted to di«s having but a

Ok«. He.

•msU clearance angle where any rounding of the surfaces would
Dot be allowaUe.

Shearing. Die. blocks have their cutting edges beveled in
<ffder that the blank nuiy be cut from the stock by a shear-
ing cut. Shear b given the face of the die to reduce the power
necessary to cut the blank from the stock, so that a tiiieker
blank can be cut. The shear also reduces the strain on the
puntii and die.

TOOL-MAKING

201

The face of the die is sheared when the blank, or piece forced
through, is the product to be saved. But if the piece surrounding
the blank is to be saved, and the blank is of no use, the face of the
die is left perfectly flat
and the end of the punch •
is sheared

The cutting face of
the die may be sheared
by milling or planing to
the desired angle, depending on the thickness of the stock to be
punched and also on the power of the press. A common method
of shearing a die is shown in Fig. 320, which shows a section of a die
used for punching a heavy spring. The end of the punch is feft flat.
The punching, commencing at the center A, is continued with a
gradual shearing cut as the punch descends until it reaches the

Fig. 320. Die for Punching Heavy Spnng

« Fig. 321. Forging Requiring Extra .\inount of Power

ends BB, of the opening. The blank punched will be straight^
but the stock will bend somewhat unless it is quite stiflP, in which
case it springs back to shape when the pressure is removed,

When the punching requires an amount of power in excess of
the capacity of the press, as in the case of the forging shown in
lig. 321, it is necessar>' to trim the flash occasioned by the process

Fig. 322* Piece Forged and End Punched at Same Time

of drop-forging, and at the same time to punch the end to shape,
as shown in Fig. 322. It is obvious that the material removed is
not the valuable part, and, as it is necessary to use a light press,

202

TOOL-MAKING

the die may be given a shear as shown in Fig. 323, thus making it
possible to do the punching on a press whose capacity would not
be equal to the job if the die had been sheared as shown in Fig. 320.

Fig. 323. Shearinc Die for Preceding Piece

In order to facilitate the operation of grinding th^ face of a die,
it is frequently made with a raised boss around the hole as shown
in Fig. 324.

Sectional Dies. In order that dies may be worked to shape
more easily, they are sometimes made in two or more pieces which
are fastened together when in use. The plain die. Fig. 325, is
made in two pieces, which are held in their relative positions by
the dowel pin at each end, shown at A and B; when in the die holder,
they are held together in such a manner that they cannot spread.
Dies of thb form should have the surfaces that go together
finished true; the pieces should then be clamped together, and the

dowel pin holes drilled and
reamed. They should then
be taken apart and any burrs
caused by drilling and ream-
ing removed^ The pins should
now be inserted, and the t6p
and bottom of the die planed.
The outlines of the piece to
be punched are next laid out,
and the round hole at one
end drilled, after which it
should be reamed from the

back with a taper reamer to
Fif.W4. Bo« MouiMi Hole (or Qrinding gj^^ clearance. The die is

then taken apart, and the opening cut out on the planer or
sbaper, the sections of the die being held at the proper angle to
give the desired amoimt of clearance. After the two pieces have

> ■ - J

J-1 I it

TOOL-MAKING

203

been put together, the opening may be finished to the templet witb
a file and scraper.

To hold the die together securely, it is necessary to use a die
holder of the form shown in Fig. 326. The die is represented in

Fig. 325. Two- Piece Die

place in the holder, which is held in the bolster, this being in turn
attached to the bed of the press. When the die is finishied to the
templet, and the proper clearance given, make sure that the walls

Fig. 326. Die Holder

of the opening are straight (not crowning), although it is not always
considered advisable to carry the clearance to the edge, as the
size of the opening would then increase every time the die was
sharpened. In such cases the clear-
ance extends from the bottom to
within a short distance (about ) inch)
of the cutting surface, as shown in
the sectional view. Fig. 327. In'this
figure the clearance, is exaggerated
to illustrate the idea more plainly.
The walls of the uppet part of
the opening are at right angles to the base of the die; but they
must be straight (not crowning) because if the. opening is wide
enough to allow the punch to pass through the crowned part, the

Fig. 327. ClearaAce of Dies
Exaggerated

304 TOOL-MAKING

stock would, if thin, be likely to lesve the IJank with ragged edges
which would extend up on the sides of the punch and have «.
tendency to burgt the die.

Hardening Dtet. ApjJied to Ordinary Skapei. Before hard-
ening, the stripper and guide screw holes should be drilled and
tapped, and the hole drilled for the gage pin or stop. If the
name of the part to be punched, or the shelf number of the die
is to be stamped, it sliould be done now. After all screw holes
stop-pin holes, etc,, are filled with fire clay mixed with water to the
consistency of dough, the die is teady for hardening. Extreme

care should be exercised in the heating; the heat must be no
greater than is absolutely necessary, and it should be unifoml
throughout— the comers of the die must be no hotter than the
middle of the piece, end the outside surface must be of the same
temperature as the interic^r of the steel. The water in the bath
should be slightly warmed to prevent any tendency to crack. The
die should be lowered into the bath and swung back and forth
gently so that the bath may .pass through the opening and huden
the walls. As soon as the unging ceases, the die should be
removed and plunged into a tank of oil and allowed to remain
until cold, when it is brightened and the temper drawn. If more

TOOL-MAKING 205

than a few minutes are to intervene between the time the die
becomes cold and the time for commencing to draw the temper, the
die should be held over a fire or placed where it can be heated, to
remove the internal strains which have a tendency to crack the piece.
. When there is a heavy body of metal around the openings in a
die, and a light partition between the openings, there b danger of
cracking during the hardening. In such cases it is frequently
possible to apply a h'ttle oil to the light portion, especially at the
point where it connects with the heavier portion, thus preventing
too rapid cooling' of the parts, and so doing away with the danger
of cracking. The oil may be applied by means of a piece of cloth,
which may be attached to a wire; in this way the oil reaches the
desired spot and no other. The oil having been applied, the die
may be cooled in the bath in the usual manner.

Applied to Special Shapes, When a die of such a shape that
it b likely to give trouble, is to be hardened, much more satisfactory
results will follow if the pack-hardening process is used. Run
the dies from one to five hours in the fire after they are red hot;
then dip them in raw linseed oil and swing them back and forth
to force the oil through the opening. Dies having openings that are
perfect circles may be left a trifle small until after hardening, when
they are ground to exact size as shown in Fig. 328. Here the die is
held in a chuck and the grinder is motor driven.

Tempering. A very common method of drawing the temper
of dies and similar pieces, is to heat a piece of iron to a red heat
and place the hardened piece on it, leaving the face of the piece
uppermost. Experience shows, however, that this method of treat-
ment is too harsh for hardened steel, especially if the job is in the
hands of one not thoroughly experienced, for it subjects one side
of the piece to an intense heat while the opposite side is exposed
to the cooling effects of the air. If an open fire is used, a plate may
be set on the fire, and the die placed on the plate before it is hot;
now the temperature of the plate may be raised gradually, the die
being turned occasionally. In this manner, the temper can.be drawn
to the desired degree with safety. When such a fire is not available,
two plates may be used, one heating while the other is in use. The
first one should not be very hot, the next somewhat hotter, and so
on until the die is drawn to the desired oolor.

209 TOOL-MAKING '

Punches. The punch b used to force tfaemetal through the
die, thus producing pieces of the deaired ahape.

In the caae of small plain dies, the punch isgenovUy made
of the fonn shown in Fig. 329. The end ^ is of the same outline
as the opening in the die; the shoulder B which bears against the
shoulder of the puneh
holder, takes the thrast
when the pundi is woA-
ing; the shank Ctitsthe
hole in the punch holder
or in the ram of the

in most shops in this country to make the die to a drawing or a
templet, and then to harden it, after which the punch is fitted to it.
Lajfing Ovl. The templet may be used in laying out the punch
for a plain die. If the shape of the opening in the die is the same
OD each dde, Fig, 330, and the die does not change shape in
hardening, either aide of the templet may be used next to the face
of punch; but if the outline is of the form shown in Fig. 331, it will
be necessary, to exercise care to see that the proper side is used,
because the side of the templet placed against the face of the punch

Fi«. iaa. Typiul Dm Hi Sane Bbtv

when laying it out will be opposite to the one placed agunst the
face of the die when laying that out.

In order to obviate this trouble, many tooMnakers lay out tjie
face of the punch from the opening in the die before beveling tiie
face for shear. In order to hold the punch and the die together
so that there will be no danger of the punch slipping while the shape
is being transferred, a die clamp of the form ^wn in Fig. 332
^uld be used.

TOOL-MAKING

207

Maekimkg to Shape, The pfunch blank^should be machined
on both ends, and the shank turned to size. The end which is to
fit in the opening in the die should be finished with a smooth, flat
iurface, and colored with blue vitriol. After coloring, it may be
clamped to the face of the die by means of the die clamp, and the
outline of the punch mark^ on the face by scribing through the
opening in the die. This outline should be accurately marked
with a sharp-pointed prickpunch, as the scribed line is likely to
become obliterated by the various operations of machining the
pundi to shape.

MiUing or Planing. After the out-
line has been carefully prickpunched, the
punch is ready to be milled or pUned to
shape, leaving enough stock at all points
to shear into the die. If the punch is
milled to shape, the irregular surfaces
may be produced by means of a fly cutter.
Fig. 333. If it is planed, it may be held
in a pair of centers, as shown in Fig. 334,
in a shaper. If the die has been left oft
to permit laying off the punch, it should
now be beveled for shear, and hardened.

Shearing'In. The punch should be
machined close to the lines, and then
placed over the hardened die and forced
into it a little, about ^ inch. This is
termed shearing-in, and is a customary
process in this country.

Filing, After the punch has been sheared-in for a short distance,
it may be removed and worked to size by means of chisel, file, and
scraper to the witness mark, as the portion sheared-in b termed.
The operation of shearing-in may be repeated until the punch
enters the entire length.

Fit of Punch in Die. If thematerial to be punched is thin
or soft, it is necessary to make the punch a closer fit in the die than
if the stock is heavy or very stiff. Thin stock requires a punch
nicely fitted to the die in order to avoid ragged edges on the punched
blank When punching brass stock { inch in thickness, the punch

Fig. 332. DiV Clamp

20S TOOUMAKING

•hould be .0075 inch smaller than the die, the usual difference being
6 per cent of the thickoess oF the stock for brass, and 7 per cent
for steel. If the stock is very stiff, a greater difference should be
allowed, the exact amount depending on the nature of the material
to be used and the character of the tool.

After the punch has been fitted to the die, the cutting end should
be faced off to insure ■ good working surface 'and sharp edges.
Any distinguishing names or marks necessary, should be stamped
on it, after which it is ready for hardening.

Hardening. Punches are hardened by heating thetn in an
oven furnace or in a clear charcoal fire, to a low red, and cooling

ni.au. BhipiiiflbalViioliwIlhFliCiilur

in water or brine, preferably the latter. Punches whose form
insures strength, need be hardened only on the end; the hardening
should not extend quite" back to the shoulder or shank. Small,
slender punches are sometimes hardened the entire length, especially
if they rre to punch stoctC nearly as thick as the diameter of the
tool itself, for otherwise they would become upset when used.

It is generally considered good practice to haye the punch softer
than the die; on this account it is usually drawn to a color that
insures this result. If a die is drawn to a straw color, the punch
is drawn until it assumes a distinct purple, or even f> blue color.

TOOL-MAKING 209

The punch b sometimes left soft — not hardened at all; when this is
done, it can be upset, and refitted when worn. As this would

m. 334. BhwitM PuiKh in t Shim

not work satisfactorily in many cases, it can be recommended only
when a soh punch is advisable.

Special Problems In Puiichin(. Punching HoU in Pitee
Machined to Shape. It is occaidonally necessarj' to punch a hole
ill a piece of work that has been machined to some given shape.
The piece is placed on the face of the die against locating points,
or in an opening in a gage plate, the opening being of tb« same
outline as the piece of work. In ________^^^^

Fig. 3.35 is shown a blank intended ||||||i " " " ' I

for a gunsight leaf; A shows the llllll| I

blank before the rectangular bole is ^

punched, .while B represents the leaf --^

after punching.- The hole is punched ( ) ' ""' 1

somewhat smaller than finbhed size, \^^

enough stock being left to work to 3

size with broaches. |||{{|l{| r-' "'"""~ T

When punching work of thb IIIIIIIH I I

description, it is necessary to leave ^^^ o„n-,M w Pu.,.w,„
the face of the die flat; tlie punch is

sheared as shown in Fig. 336. The piece punched from the leaf is
of no value in this case; consequently, the Face of the punch a

210

TOOL-MAKING

beveled, and the face of the die is left flat in order that the sight-
leaf may be straight after punching.

, Use of Stripper, When a die and punch arc to be used for an
operation similar to the one just described, it is necessary to make
a stripper of a form that allows the pieces to be easily placed in
position and removed. As the piece which is punched is likely
to increase nn width from the operation, it is advisable to have
stops or a guide on one side only, in order that the piece be readily
removed after the hole is made. Fig. 337 shows the die with stripper
and guide attached. The stripper is raised sufficiently from the die

to allow the work to be readily
inserted. A gage pin is furnished
for the end of the piece, to de-
termine the position of the slot
in relation to the end. On one
side is a guide against which the
piece rests to bring the slot into
a central position, the piece being
held by means of a screwdriver,
>X] a thin piece of steel, or a piece
^^^ of wood.

When the size of a- piece to.
be punched does not allow the use
of a stripper attached to the die,
as in the previous example, the
stripper may be attached to the
punch. Fig. 338. It is made in such a manner that the stripper
plate, descending with the punch, comes in contact with the piece
being operated on and remains stationary; between the stripper
plate and the punch holder are coil springs which are compressed.
The punch passes through the piece and returns, arid the stripper,
being forced downward by the action of the springs, forces the
blank from the punch. The gage plate which is securely fastened
to the die by screws and dowel pins, as shown, has an opening
of the same general outline as the blank, but somewhat larger, in
order that the blank may be easily put in place and removed.
Puruihing Incomplete Holes, It is sometimes necessary to punch
til hole incompletely, leaving the portioa puDched put attached at one

Fig.^336. Sheared Punch-

TOOL-MAKING i\%

end, as shown in Pig. 339. If several holes are to be made in the
piece, the punches may all be attached to one holder, and all let
into one die block. This method of punching is resorted to when

-l

° (Q

0) o

® L

J ®

manufacturing skbtes,
^aped by subwquent
toa clamps.

bent down from the plate is
provide a bearing for the

212

TOQlr MAKING

Piercing and Curling. A very satisfactory form of piercing
and curling die is illustrated in Fig. 340. The various stagies of
the operation of punching, piercing, and curling are shown at a, b,

and c. At a the punch is
starting to pierce the sheet;
J> shows the punch having
pierced the stock and start-
ing to curl the loop; e shows
the loop curled up against
the sheet. If it is considered
necessary, the punch may be
set to go lower and curl the
loop inside of itself, as shown
at d; or the end of the punch
may be flatted somewhat, as shown at e, and a loop formed as
shown at /. This die may be made multiple, and any number of
loops (within the capacity of the press) made and formed at one

Fig. 339. 6h«e. Puochod with Portion Removed
Left Attached at Cue End

CcfJ

FSf. 340. Pieroiot wA Curlinf Di«

time; or pierdng and cutting-off punches may be combinled, screw
holes or other holes punched, and strips of any desired length cut
off, at one operation. A stripper plate, attach^ to either the

TOOL-MAKING

213

punch or the die, should be provided to strip the work from the
punch. If attached to the die, the stripper must be high enough
above the face to permit of easy removal of the work from the
openings of the die.

-OangDies. The gang die is designed to punch m one operation
the blank itself and also any holes to be made in the bUnk. Two
operations would be nec-
essary if a punch and
die of the form shown
in Fig. 338 were used.

A common design
of a gang die b shown
in Fig. 341, which rep-
resents a die for the
piece operated on in
Fig. 338.. The stock is
fed from right to left.
The sheet rests against
the guide C, and is so
located that the end
slightly overlaps the
first edge of the opening
R. The two holes F
and F* are punched,
and the end of the
sheet is trimmed by the
punch A to furnish a
locating point to go
against the stop D, At
each stroke of the press
a blank is produced
and the two holes are
punched. For the next
blank the gage* pin D should be located about .010 inch
farther to the left than the' proper location for punching. The
center pins, as they enter the holes, draw the stock back to the
proper location. It is obvious that the punch A must be a tnBt^
longer than the punches B' and B; were the small punches longer

Fis. 341. QMig Di*

TOOL-MAKINQ

than A or even of the same length, they would hold the stock in
such a manner that the centering pins could not locate it, and,
moreover, the centering pins, striking on one edge of the hole,
would spoil the blank punched, and probably cause the pins to
break. The centering pins must not be a tight fit in the holes,
or the punched blank will stick to the pins and return with the
punch. By carefully fitting the pms to a punched hole, punching

<D o

® o

cd( ) O O

•

Fi<. 342. Punch and Di» Which Cut Away Scrap

within a very small limit of variation can be insured; in fact,
for most classes of work, it is possible to punch near enough
to standards for aU practical' purposes.

When a gang die of the design 3hown in Fig. 341 is used to
punch a strip wider than is necessary to get out two punchings,
it will be readily seen that the scrap left between must be removed
vy some means. This is frequently done by a large lever shear

TOOL-MAKING 213

or a pair of power shears, but that is a costly operation where many

pieces are punched at a time. To avoid this extra cost, dies are

made with an extra opening,

and & punch working into

this cuts away the auiplua

stock or scrap,- leaving the

edge of the sheet straight and

in condition to rest against

the guide. In Pig. 342, the

opening A is the trimming

die; the punch working in this

cuts away the scrap, leaving

the edge of the sheet straight. p,, 3,3. p^,,, aMt, u. prev«u Uo«.ini

Ai times, punches set in
a holder. Figs. 341 and 342 have, a tendency to loosen and draw
out of the benriiig. A method for pre\'enting this is shown in
Fig. 343, an angled block pressing against the punch shank A-

When a die be«>mes worn through use so that the opening
is large, it ma/ be placed in the fire, brought to a forging heat, and
the opening closed with a "fuller". Fig. 344. After being aunealed.

216 TOOL-MAKING

the die can be worked out to size and hardened. la this way dies
can be worked over several times. Fig. 345 shows ■ die with the
core sawed out by means of a power saw. Fig: 218.

Punches with Qulde Bushli^s. A great amount of trouble ia
experienced m some shops when attempting to use small piercing
punches to produce boles in stock as thick as the diameter of the

punch, or thicker. This difficulty can be obviated by UMUg guide
bushings in the stripper plate to support the punches and guide
them to the opening in the die. The bushings should be made

TOOL-MAKING 217

from tod steel, haidened, the holes ground and lapped to aa exact
fit for the punches; or, in the case uf very small punches, where
grinding is out ot the question, the hole may be lapped to size,
and the outside ground to size to force it into the hole in the
stripper plate.

The guide bushings must be in exact alignment with thb open-
ings in the die, Kg. 346 shows a form of die provided with guide
bushings bb, for the punches aa. The dies «; are made from tool
steel, hardened, and forced into a machine-steel die block. The
punches are made from drill rod and are held in place by binding
screws dd and adjusting butt screws te. Between the binding screws
d and the punch, at the end that bears against the punch, is a piece
of wire of semicircular shape. This allows the punch to be set down
as the punching end is ground away.

In the case of gang punches and dies, used
in the production of perforated ^iheet-metal work,
which have sometimes several hundred pietcing
punches working into one die. it is customary
to provide each punch with a guide bushing.

Punches with Tapered Sectbn for Spreading.
Trouble is experienced at times with blanking
and piercing punches because the metal clings to
tjie punch and pulls the end olT in the operation
of stripping. This is especially the case when a t„ ,., p^^ r^.
clinging metal is being worked. The trouble MnedtorriuiiDi
can be avoided by making the punch of the design
shown in Fig. 347, where the portion marked a is straight and the
deMred fit in the die. The portion b is tapered and smaller at its
junction with a. When the die ia set up in the presa, a enters the
die nearly its entire length: the tapered portion b, entering the stock,
spreads it, thus enlargiiig the opening, and so preventing it from
binding the punch during the process of stripping. It is of course
necessary, when setting a punch ot this design in the press, to make
sure that the tapered portion does not enter the opening in the die.

Multiple Die. If the shape of the pieces to be punched allow*
it, it is sometimes advisable to make several openings in the die
of the same outline so arranged that as many pieces may be punched
ft a time as there are openings in the die block. This -will effect

'dl^

TOOL-MAKING

a great saving where work is punched in large quantities. In th«
manufacture of perforated sheet-meta! work, it is customary to
make dies having as many as iiye' hundred punches working into
one die block at a time; but as thb is an unusual application of this

principle, it will not be
considered.

If it is necessary to
punch ten holes in the
piece shown in Fig. 348^
a die can be made hav-
ing this number of open-

ooooo
ooooo

Fig. 348. Sheet-Metel Blank

ings. Then, by making
a punch holder having
an equal number of punches properly located, all the holes can be
puiidied at one stroke of the press.

While in the case just cited the piece of stock which had the holes
punched in it is the product, the- punchings being scrap, the same
principle can be applied to punching blanks from a sheet of stock.
The design shown in Fig. 349 is the product in a shop where many
thousands of this piece are used monthly. The die produces a
dozen or more blanks at each stroke of the press, but for convenience
in illustrating the die and punches, but four openings in the die,

with a corresponding number of punches are shown,

Fig. 350.

If a die were made with the openings near
enough together to punch the stock, Fig. 351; there
would be so little stock between the openings that
the die would not stand up when used; for this
reason the openings are located in such a manner
that every other opening is omitted. When the
punch descends, four blanks are punched, and,
the stock is moved until the first opening strikes the
gage pin, Fig. 350. This leaves the stock in position
to punch between the openings already made. The next time the
stock is moved until the gage pin strikes the wall of the last
opening to the right.

Bending Die. In order to bend metals to various forms, dies
are made for use in punching presses, drop hammers, and various

Simple
»lv

Tw«lve

Stumping
Produced at a
Strok»

TOOL-MAKING

219

other machines. A simple form of bending die is shown in Fig. 352.
The shape of the upper and lower parts of the die is such that when
the upper part is brought down on the blank B (shown by the dotted

o o

"""'"" "N- — — -.— — — — «- — .i- — -, .- —

•

—

Fig. 350. Gang Punch »n<l Die for Simple Punching

lines) that will be bent to the required shape. The shoulder A forms
a locating stop, against which the blank rests before bending.

Dies for extremely soft metals may be made of the exact shape
of the model, or the shape the piece should be when finished;
but if the piece is of stiff material which bends with difficulty, it will
be necessary to make the

die of a form that will
give the article wore bend
than is required, as the
piece will spring back
somewhat as soon as
released by the return of
the upper part.

The bending of articles of certain shapes requires tools so
designed that certain portions of the piece will bend before others.
Any attempt to make the tools solid, and thus to do the bending

Fig. 351. Punchings Too CloM Together

220

TOOLrMAKING

Fif . 3A2. 8iiiM;»l« Bendinc Die

of the various portions at once» would result in stretching the stock
As a rule it is not advisable to stretch stock, and dies are constructed

to do away with this

trouble.

Bending Die for

* •

Rijfht Angles. Under
certain conditions a bend-
ing die which has a hor-
izontal surface for the
work to rest on and a
vertical-sided punch does
not work in a satisfactory
manner — this is espe-
cially true when the stock is stiff. In that case, a die of the design
shown in Fig. 353 works well, as the angle may be made other than
90 degrees to aUow for the spring of the metal.

This design of die may be used for angles other than right
angles. It is especially satisfactory for bending springs and other
pieces made from a stiff stock that is liable to spring back somewhat
after bending, as the lower block may be made with an angle greater

than 90 degrees to allow for
this factor.

Bending Die for Light Work.
For comparatively light work,
the form of bending die shown
in Fig. 354 is very satisfactory,
and may be used for a variety
of shapes and angles. The die
block a is drilled and reamed
to receive the shouldered por-
tion b. The rectangular groove,
to receive the pad, is milled or
planed, and the pad is fitted
and forced in. The proper angle
or shape is then milled in tfie block a and pad 6. The surfaces are care-
fully finbhed and the pad forced out and drawfiled until it slides nicely
in the groove. The spring c forces the pad against the washer d.
G4ge plates are provided to locate accurately the pieces to be bent.

Fif. 353. Beodins Die for Right Aoglei

TOOL-MAKING 221

Tig. 355 shovs a die, the upper part of wliich has the portion a
so coHstnii^ed that it engages the stock first and forces it down
into the impresaon in the lower
portion. The rewstance of the
coil spring is then overcome,
and a is forced up into the
opening provided for it. The
arms ee bend the ends of the
piece. After bending, the arti-
cle is of the form diown Bt b.

Compound Bending Die. In
Fig- 356 is shown a form of die
used in bending bow spring and
looped wire for armature con-
nections or other looped wire-
work. The work is placed in
the die, and the punch, as it
descends, bends the wire to the
shape of the die. The spring
just hack of the punch is com-
piessed; thia allows the punch
holder to descend and force the
side benders BB toward the
puiichbj'meansof the wedge pins
A A, and thus forms the
piece into a circle. Fig.
357 shows the punch when
down. It is obvious that
if is necessary to make
theshapeofthepunchand
die ditferent. The lower
die must haveits bending
surface s curve of a
radiusequal to the ra.cius
of the punch plus the
thickness of the material. ^ ^^ ■^""' ' — "" "~ "

Forming Die. I'his type of die is familiarly known as a (£
die. The most common exampleof the forming die a that u

222 TOOL-MAKING

drawing a flat, drcular blank, shown at A, Fig. 35$, into a cup-
shaped piece,3hown at B. This operation can be done in an ordinary

punching press by means of a forming die of the shape known as a

pugh-through die, so called from the fact that the piece is formed

to shape and pushed through the die at

one operation. This form of die is shown

in Fig. 359. The face of the die is cut

to receive the blank; this depression is

known as the "set e<lge". The opening

in the die is given a "draw" of from J .to J of a degree, making it
larger at the top; the up^wr edge is rounded over and left very

TOOL-MAKING 223

RDOoth, knd the bottom edge b made very sharp, in order that
the piece may not be carried back with the punch as it returns.

This fonn of die is left as hard as possible, and the walls of the
(^wningaremadeassmooth as the^ can be polished. It is sometimes
advistble to finish the walls with a lateral rather than a circular

Hardening Drawiiq; and Redrawlnf Diet. Drawing and
redrawing dies having holes which pass entirely through them,
■s shown in Fig. 360, give considerable trouble when hardened unlesa
proper methods of treatment ale used. The [uincip^ difficulties
experienced are alteration
b the siie of the hole,
and soft spots in the
walls of the holes.

As there is do need
for the exterior of the die
being hard, the whole
attention of the hardener
should be given to getting
the walls of the hole ss
hard as possible, as this
portion is subjected to
conuderable strain and to excessive abrasive action, and soft
portions render the die useless. This is especially true of dies used
for such work as redrawing cartridge shells and similar pieces.

In order to harden the walls of the hole, and yet leave tlie
drcumference of the die soft, it is necessary to make a fixture to
cover the portions desired soft. Such a fixture is shown in Fig. 360.
Tt may be made from a piece of cast iron, the portion A being a little,
say 1 inch larger than the diameter of the die. The opening to
receive the die sliuuld be ^ inch larger than the die. The balance
of the hole should be somewhat larger than the hole in the die, say
\ inch. A cover may be made of the same material, and it should
be a loose fit on the holder. The hole in the cover should be \ inch
or more larger than the hole in the die and beveled as shown.

When the die is heated to a uniform red, it is placed in the
fixture, the cover put on, and the whole held under a water pipe,
or fnucet. Fig. 362, while the water is aUowed to flow through the

TOOL-MAKING

KiK. MW.

I'biturp for Cuvcriiis Soft
I'ortioii oC Dii'

hole as shown. A mistake sometimes made consists in placing the

fixture in a bath and then attempting to force the water through

the hole; unsatisfactory results
always follow if this is done, for
the water cannot flow through
the hole, pockets of steam form
which prevent hardening, and
soft spots result. The fixture
should not be immersed in water,
but should be held so that the
water can pass unretarded
through the hole and carry the
steam with it. The water supply
should be sufficient to fill the hole
and should pass through under a
fair head, but not too swiftly.
This method, when properly executed, gives excellent results.

As a rule, dies of this kind are left dead hard, the temper not being

drawn at all.

Reversed Die, The die
shown in Fig. 3G2, known as a
reversed die, is extensively used
in many shops for heavy punch-
ing on such work as washers,
ball seats, etc. Under many
conditions, it works much better
than a gang die, and it is simpler
to make than a compound die.
The punch A is made the
size of the diameter of the washer
to be produced, and is hollow to
receive the punch B which pro-
duces the hole. The scrap from
B passes up through the punch
y| and through the outlet shown.
The washer blank remains in the

die C until forced out by the ejector D, which is automatically'

bi)erated by the press.

KilE. 3«l

Mctluxt uf Uduieniniz a
RcdruwinK Die

TOOL-MAKING 225

Con^Muad Dies. In Fig. 363 ia shown a die used in producing
a washer and punching a hole in it at one operation, thus insuring
a blank with a hole that is exactly central. The work from a dte
of this description a better than that done by the gang die. It is
espeddly adapted for thin sheet metal, paper, and mica parts.

Tbe upper die A receives the lower punch B, while the lower
opening C receives the upper punch D. The stripper £ forces the

blank out of the die; while the stripper F forces the sheet off
the punch B.

The die shown Is f6r punching a round washer, but the tool
may be made for producing pieces of complicated and irregular
form. It proves especially valuable when ui<ed in connection with
a sub-press.

Triple Dies. When it is necessary to punch three or more
holes in a tubular or other shaped piece where this form of die can
be used, a triple die effects a great saving, as the holes can be punched
at one stroke of the press.

226 _ TOOL-MAKING

Fig. 364 nhows a die used for punchin); three holes in n tube
and is intended for use in any simple power press. The dies AAA
are placed in a hollow stud which fits in the inside of the piece to
be punched. The vertical punch is held in. the punch holder as
shown. The horizontal punches are operated by means of the
inclined arms CC, working in the horizontal sUdes BB.

The horizontal punches in the illustration are made from
drill rod of the desired size; but they may be of any desired form.

the opening in the die being made to match. Where work is done
in batches sufficientl.i' large to warrant the expense of a triple die,
its construction is to be recommended, as better results can be
obtained than if one hole is punched at a time. '

Follow Dies. The name follow die is given that form of die
where the pieces are blanked and bent at one opemticin. In Fig. 365
is shown a punch and die used in producing the piece shown at the
left. The two holea in nrie end an<l the opening at the opposite
end are punched, and the piece bent to shape, at one passage through

TO0I.-MAKINC.

tlie press. Tlie briidiiig. picroiiiKt i
uttHclied to the same Iiolilcr aKsliDiv

i'iittiii{!-oir punches 8 re
I) tlie upper part of the ci

ir the stock to be punched is soft, the beiitlinf; portinn of the
punch anij ijie may be made nearly the shape of the desired piece;
if, on the contrary, the stock is stiff, they must be made of greater

xt;F7.

„ Oi»r.lu.n

"After Curling". The loops on hinges and m
ol its work. The stock is first punched o

22S TOOL-MAKING

angle to allow the piece to spring back after punching. The amount
to be allowed cannot be stated, but must be detennined by experi-
ment. Thia test may be
made while the die la
soft, at which time the
piercing or mtting-off
portions must not be
used. Dies of the type
under con^deratipn ^ve
best results if liardened
by pack hardening.

Curling Dies. These
dies are used in fonning
a loop such as is shown
I Vig. 366 and marked
ailar pieces are examples
: as shown at the upper
left-hand comer, and the
blunts are forced into a
curling die of the design
' t^liown at C. The punch
D has a V-shaped im-
pre^ion in its face, as

In making this die,
the block C is machined
to size. The hole £ a
drilled, reamed, and
lapped to size; the lap-
ping also produces a
smooth hole, i( a round,
revolving lap of the right
size is used. The slot F
F 3U7 A iht F r c 1 Di '^ then milled.

If the stock is com-
paratively soft or b eauly bent, and if the die is to be used for but
a few holes, it need not be hardened; if intended as permanent equip-
ment, it must be hardened, preferably by the pack-hardening process.

TOOL-MAKING 229

Anotlier form of curling die, Fig. 367, is used in curlini; a loop
afDuiid the end of h circular shell or vessel. The stock entering
the circular'shapett portion of the punch is made to confoitQ to the
uze of the circle.

WWng Dies. AViriiig Hies are similar in construction to curling
dies. They are used to curl the upper edge of a vessel which is
in the die. or holder, and lies on the top of a spring-supported rinj; C,
Fig. 308.

As the punch de>ioends, it depresses the ring C and
curls the upper «dge of the vessel around the wire ring, ns
shown nt B.

230 TOOL-MAKING

Comppund Punchiiq: and Btniiag Dies. In Fig. 369 are shown
three views of a punch snd die for cutting oR and bending to shape
at one operation a piece of special form; D is the finished piece.
This form of die can be used fur a variety of work, and it is recom-
mended wherever the work is done in sufficient ((uantities to warrant
the expense of the tool.

•4 is a view of both punch and die, showing also the punch
holder and bolster; ij, shows the stripper used in knocking the
finished piece from the bending punch; the cutting-off portion is
seen In side elevation. Thestockisfed through, anij strikes the atop.

The cut-off is slightly longer than the arm of the bending die. in
order that the stock may be cut ofl before the bender reaches it.

. The stripper is a horizontal plunger actuated by a coil Spring.
Thb plunger has a pin through the back end to prevent it going
too far, while another pin extends through the enlarged portion,
against which the spring works. The inclined arm fastened to the
punch holder will, when descending, force the plunger back and
oft the face of the bending punch. C is a top view of die.

There is fufficient space between the upper surface of the cutting-
off die and the stripper so that the stock can pass over the plunger

TOOL-MAKING

231

stripper. The inclined arm which operates the plunger stripper
pushes this out of the way before the descending punch reaches
the stock.

After hardening, the cutting-off die and punch are drawn to a
full straw color, and the bending part to a brown. When the
cutting and bending parts are of complicated design, best results
follow if they are pack hardened. The stock is purchased with
the desired width, and the pieces punched and bent with no waste
of stock.

Progressive Dies. Fig. 370 shows a die used to bend a caliper
bow to a finished circle. This type of die may be used to produce
pieces that are square in form, or of any one of a variety of shapes.
It is generally necessary to resort to one or more preliminary bending

Fig. 370. Progressive Die for Bending Caliper Bowi

operations to get the pieces to a form that makes it possible to bend
them to finish form in the die shown. Since one or more dies are
used before the final finishing die, and since one operation leads
to another, dies of this class are grouped under the head of pro-
gressive dies.

The bow a, Fig. 371, is made by first punching a blank of the
form shown at b. The ends of this blank are then bent separately,
l(nd shown at c and d. The piece is finally bent to the shape a by
means of the die under consideration. It will be noticed that the
forming portion of the punch projects out from the body and is
provided with clearance space above it, in ofder that the ends of the
piece may bend around it, and against one another if necessary.
While the example of work given is simple, yet pieces of intricate
sluipe can be produced by means of dies of this kind.

TOOL-MAKING

Another example of progressive dies and the work done witli
them is ^own in Figs. 372 to 37S. when- Fig. 372 shows the die

)

(

ft)

used in pierdng the hole, in forming and cutting off the ends, i
producing a blank of the form ^howii in Pig. 373. The stock u

^^i

ia ribbon copper of thedesired width of piece; this is purchased in coils
and ted to the die shown in Fig. 372, by an automatic feeding device.

TOOL-MAKING 233

The pieces are next bent to form, Fif(. 374, by m«ana of tbe bending
die and punch. Fig. 375. The third opertition h done by means

o o

^aaar

n-n

B ii lilMW 11 R

of the punch. Fig. 376, and
the die. Fig. 377. The punch
A, Fig. 376, folds the piece
shown in Fig. 374 around the
projecting portion and forms
it to tlie shape shown in
Fig. 378

Although it might be
possible to bend a piece of
this dKwripUon in a com-
pound bending die at one
operation, it is doubtful if the
ultimate cost would be any
less than that of the indi-
vidual operations, as the cost

of Upkeep would be much ^-^ j„ f,^^^, ,„, b,„4i^ c^^ atrip
greater,aiid the process some- " ""^ *"«•

what slower. There are many jobs where it is advisable to use com-
pound bending dies; but where there is no saving in cost of labor,
9T where the presses are not adapted to their use, it is best to resort

TOOL-MAKING

to methods particularly suitni to llie itidividiiel job, e
necFs3itftt«3 a greater number of operation:].

Sub-Press Dies. A sub-press is a small self-contained press
which is operateil by a large press. It is extensively used in watcli
and clock «hop3 for punching the move-
ments. Fig. 379 shows samples of work done
on this press. Figs. 380 and 381 show dilTer-
ent styles of sub-presses.

While sub-presses differ in design, the
pattern illustrated in Fig. 332 is well adapted
for general use. The upper portion A of
the press, as shown in cross-section, is bored
out tapering to receive the Babbitt sleeve,
and the feet are bored to fit on the base.
A thread is cut at the top to receive the nut
used in holding the Babbitt lining tightl.v in
place. The die goes in the base, and is
' ^^coi^t^iS^''" "' made in the usual manner. The punch,
which is held in the plunger B, is carefully
:, and the space around the plunger is filled with Babbitt
^tnl, poured in the usual manner. In order that the [hunger
all be held from turning, three or tour parallel grooves *K

TOOI^MAKINO 236

milled as shown, before the Babbitt metal is poured, the latta,
filling the grooves, acts as a guide.

The slot at the top of the plunger engages loosely in the gate of
the press, so that absolute accuracy in the working of the ram of the

fcO-^

press is not essential. A good press, however, is always to be pre-
ferred. It b considered good practice to adjust the press so that
the punch does not actually eater the die, but comes just far enough

to punch the blank out of the stock withput the edges of the die
and punch coming in contact.

The sub-press is especially valuable for complicated dies, and
many compound dies are used in this form. Complicated dies,
which, when made in the ordinary way, would produce but a com-

238 TOOL-MAKING

paratively few pieces, will, when 3ub-pi«3sed, punch from 20,000
to 50,000 pieces.

Um of High-Speed Sleel for DIei. The advisability of using
high-speed steel for punch-press hianbing, bending, forming, and
other dies, depends in a large measure oti the facilities in the indi-
vidual shop, for hardening tools made from this steel. It conditions
are favorable, there is no doubt that manj' dies made from hi^-
speed steel will produce several times the amount of work which
the same die made from carbon steel will produce. Tbb ia espeoally

true of forming, bending, and drawing dies, where there is crushing
strain and a tendency to wear from abrasion.

In making a die, as in making many other forms of tools, the
principal item of expense is the labor; the difference in the cost of
steel is insignificant when the Hfe of the tool and the increased amount
of work it will turn out are considered.

Dies made from high-speed steel should be pre^ieated to a low
red in some form of pre-heating furnace; then placed in a hi^t-epeei]
furnace and raised to a uniform temperature of from ITHf F. to

TOOL-MAKING 23T

2l<Xf F., after which they should be removed and immediately
plunged into « bath of oil. Dies that are not to be subjected to great
strain or extreme shock may be heated to the higher temperature
meotioiKd, while those that are to be subjected to strains should
recrive lower heats. Different makes of steel require different
temperBtures on account of the varying percentages of alloys. As
a resuh, exact temperatures cannot be definitely aUted.

After hardening, the temper should be drawn from 460° F. to
530* F., depending on the strain the toot is lo receive. If the strains
are excessive, the higher temperature must be given.

Fhiid Dt*s. These are used in the production of various kinds
of hollow ware, such as vases, lamp bodies, match safes, etc. The
metal may be Britannia ware, silver, or soft brass. The die is gen-
erally a casting of soft close-grained iron. It is made in several,
parts, as it is necessary to open it in order to^gel the piece out.

238 TOOL-MAKING

Fig. 383 shows a die of this description. The plunger works
down through the knurled sleeve, thus causing the confined fluid.

with which the piece has been filled, to force the metal out into the
impressions in the mold.

It is the custom in some factories to use soft rubber In place of
the water or other fluid, the plunger pressing on it and thus swelling
the metal out into the die. It is claimed that in producing clear-
cut outlines and full, sharp cor-
ners, the rubber works better
than a fluid.
I Hollow Punches. When

' work is to be punched from
paper, cloth, or leather, hollow
cutters or dinking diia are com-
monly used. They give better
satisfaction and are more cheaply
produced than the ordinary
punch and die used for blanking.
ni.3M. Hoi loir pjrth or Tool siMi weUal Several thieltiiesses of material
""" "" may be cut at once, the punch

may be driven through the material with a maul or mallet operated
by hand, or it may be used in a press.

While the cutter may be of ordinary tool steel, it is customary
to use stock made especially for the purpose, by welding a suitable

TOOL-MAKING

239

Fig. 385. Cultins IViard to Be Attached
on tiax Oi Press

grade of tool steel to a back of Norway iron, as shown in Fig. 383,
where the metal is represented in cross-section.

In some shops, the strips of iron and steel are welded as required.
As a rule, however, better results are obtained if the commercial
article is purchased, for
the welding is done at
the steel mill under con-
ditions which insure bet-
ter material and more
solid joints.

From a templet
made for the shape of
the desired opening in the cutter, the blacksmith forms the tool, and
welds it. The cutting edge is beveled on the outside, as shown in
Fig. 384, to an angle of about 20 degrees. After welding and shaping,
the inside is filed to the desired size and sha'pe, allowance being made
for the shrinkage which takes place when the cutter is hardened.

This form of cutter can be used in a hand, foot, or power press;
or it can be used by hand. If designed for a press, it is made without
a handle, the cutter being brazed to a l^ise; the brazing material
is soft brass, borax being used for the flux. In some instances the
cutter back*is bolted to the press base, the cutting edge uppermost;
in other cases, the base is attached to the movable ram of the press,
and the stock to be cut is placed on a board on the base of the press.
This board is made by gluing together several pieces of hard, well-
seasoned maple, the pieces being
arranged as shown in Fig. 385,
so that the end grain of the wood
forms the surfaces on which the
cutter strikes. The various blocks
should be securely held together
by bolts in addition to the glue.
After gluing and bolting, the sur-
faces should be worked down flat,
smooth, and parallel. When not in use, the board should be
dampened slightly to prevent the opening of the grain of the wood.

If the cutter is to be operated by hand, a handle such as shown
in Fig. 380 should be provided. This handle is brazed to the cutter.

Fie- 386. Cutting Die and Handle

TOOL-MAKING

TOOL-MAKING 241

luiully before IwrdeDing the tool. In many shops this fonn of tool
is called a cutting die.

BROACHES

The operation of broaching is many timea classed under the
Mme head as that of punching with punches and dies, as both may
be done in the punch press, and when such is the case, the operations
resemble each other.

Formerly all broaching was done by pushing the cutting tool —
broach — through the stock. At the present time, a form of machine

called a draw-broaching machine Is used in many shops, and
the tools are drawn through the work. It is possible, with the
draw broach, to make the broaches much longer than in push broach-
ijig, so that one broach of the former kind may be made to do as
much work as several of the latter. In actual practice, one draw
broach has accomplished as much work as twelve push broaches,
and in less than one-fifth of the time, thus effecting a decided saving
in time and cost of tools.

The process of draw broaching has revolutionized certain
methods of manufacture, especially that of producing straight
holes oF irregular form running quite through pieces of work. WhJl*

242 T00[;-MAK1NG

broaching by tneaos of push-through broaches has bern practiced
tor muiy years, draw broaching ia of comparatively recent ort^n.
The success of the method depenrls in a great measure on the design
and construction of the broach used in producing the bole.

Design of Draw- Broaching Machines. Draw-broaching ma-
chines are made of various sixes and design. For hght pieces having
short boles, a small machine designed especially for such work,

TOOL-MAKING

243

should be used, as it can be made to produce work more rapidly
than a heavy machine; but if heavy work with large or long holes
is to be broached, it b necessary to use a heavy, strong inachine
with a long pull. A small broaching machine suitable for light work
that must be handled rapidly, is shown in Fig. 387, and some

*/»H

^Losl 4 Hsoth Straight
Fig- 390 Keyn-ay Broach

samples of work done with it, are shown in Fig. 388. A much
larger machine, with samples of work it is especially adapted for, is
illustrated in Fig. 389.

Where a comparatively small amount of metal is to be removed
by the broach, it is possible to produce a finished hole with one broach ;
but where considerable metal must be cut away> it is necessary to
use two or more broaches, each a little larger than the one preceding it.

The time saved by draw-broaching keyways in long holes, as
compared with methods formerly used, is apparent when one realizes
that it takes but three minutes to produce a J-inch keyway 13
inches long by the use of two broaches. On shorter work, the
keyways can be cut in One operation. Fig. 390 shows a keyway
broach.

The ability of a broach to do a certain amount of work is gen-
erally governed by the amount of stock to be removed, as the indi-

Fic 391. Broach Teeth

vidual tooth must not cut away a greater amount of stock in the
form of chips than can be held in the space between the teeth without
interfering with the cutting. While it is customary to make broach
teeth with their backs of the form shown at d, Fig. 391, at times
it is necessary to give them the form shown at e, to provide a larger

244 TOOL-MAKING

chip space. The latter shape, however, does not give so strong
a tooth Bs the former. Many times a round hole, the diameter of
which b a httle less than the
smal1e«t diameter of the fin-
ished hole, is drilled in the
piece of work, uid the hole
brought to the deured siie
and ^ape by drawing the
broach through it.

Illustrations of Broach*

big. The piece of work shown

n* »» -K,y-«.B«>.=hrfinO»,0p-.u=. [„ pjg 392, which has fgur

j-inch keyways in a ]-inch hole 3 inches long, is brof^hed in

one operation by the use of a four-spline broach.

The piece shown in Fig.
393, made from soft steel, is
broached from a round hole
in one operation by the use
I of one broach, the time nec-
essary being one and one-
half minutes. The broach
is a hexagon 1| inches in
diameter and the hole is 3
Ri. 3»j Bnuciuni soti siKi m Our OpaniiHi inches long. If bardcT stock
is used, or longer holes broached, it may be necessary to use
two, or even three broaches to produce a satisfactory hole.

Square holes are often

broached in gears and similar

pieces at a single operation.

As a rule these holes are made

I with round instead of square

' corners. Fig. 394. This form

of hole ia designed to give

greater strength to the piece,

and is used especially where

Fit. 3B4 BiDuhini Squm ROa ^^^ j^^^^jj is to be Subjected to

great strain, and where square corners would be a source of weakness.

If necessary, the broach may be made to produce square corners.

TOOL-MAKING 245

While it b possible to broach a large variety at forms and
sizes of holes at a single operation, yet for certain jobs — as, for
instance, the piece of work shown in Fit* 395 — several operations
are required. A portion of the piece, that is one notch, is cut at
a time, the work being held in an index fixture so designed that the
piece can be turned one-sixth of a revolution after each broaching
operation, and the process repeated until all six notches have
been produced. The forging, which is 6 inches in diameter and l]
inches thick, had a hole 4 inches ill diameter bored in it before the
piece was taken to the broaching machine to be notched.

Fig. 396 shows how the teeth of an Liiteruaj gear are produced
by broaching with an index
fixture. In doing this class of
work, as in cutting keyways in
round holes, it is customary to
guide the broach with bushings.
The bushings fit the hole in the
vaik and receive the broach as
shown in Fig. 389, or are attached
to the machine and so guide the
broach in the proper location.

We have shoivn but a few
of the many varieties of work
that are satisfactorily produced
at a relatively small cost by
draw broaching.

Under certain conditions round holes are produced by round
broaches instead of being reamed. Thb is satisfactory for some
classes of work, and the cost of finishing to ^xe is much less than
by reaming.

Fig. 397 shows a broach which does no cutting. It is employed
to M»e holes in Babbitt metal and other alloys used for bearings,
where it is advisable to compress the metal to give good wearing
qualities. The broach is drawn through the same a3_any broach,
and leaves a smooth hole, true to size.

In ft great many cases, broaches of various forms are made
to start in a round drilled or cored hole; at other times the starting
■bole may be rectangular. Fig- 393, or of some other fohn where

248 TOOL-MAKING

the core tatty be drilled and broken out as shown at a. Fig. 3d9,
or the rough boles mtty be produced in the die if the piece ia drop-
fo^ed as shown at b The finished broached hole la the connecting
rod, aa shown in Fig. 398, is 4J inches long by 2i inches wide.

The length of the tuAe that can be broached with one broach
is usually twice its diameter. For instance, if the broach b I inch
square, it can be used to broach a hole 2 inches long. When the
work is of greater length, two or more broaches are required, depend-
ing, howevei; upon the nature of the metal being broached, and

TOOL-MAKING

247

also upon the form of the broach, as the larger the round corner,
the easier the pull on the broacji. If absolutely sharp corners are

Fig. 9d7. BroMh Thai Doe* Not Cut

made, the shorter will be the length of hole that can be broached,
and, in case of long holes, th^ greater the number of broaches that

Pic. 308. Connecting Rod with Rectangular Startiiw Hole

must be used. The length of the hole that can be broached
must be determined by the capacity of the machine.

if \

Fig. 399 Method of Broaching Rectangular Hole

Stock for Broaches. AUoy Steel. Broaches should, as a rule,
be made from a good grade of crucible tool steel. Several of th^ alloy

248 TOOL-MAKING

steeb work exceptionally well for broaches that are to be subjected
to heavy pulls; this is especially true of vanadium tool steel, the
vanadium renders the steel stronger and tougher, and its preenoe
in the steel also increases the range of heat that can be employed
when hardening, without augmenting the brittleness. The maou»
facturers of these steeb recommend a hardening temperature of
irom 1350"* F. to 1425"* F., grading the heat according to the diameter
of the broach. , The temper should be drawn to a full straw ooior^
46(rF.

Oil^ Hardening SteeU. There are several oil-hardening steeb
that work well for many kinds of broaches. Their nature variea
so much that it would not be wise to give specific instructions for
their use. In case they are employed, it b best to obtain instructions
for their treattnent from the individual makers.

High-Speed Sieel High-speed st^l is used for some classes
of broaches, but it is not advised unless the designer b familiar with
the limitations of thb .steel for this particular class of work. U
some cases where conditions are favorable, high-speed steel broaches
used on malleable cast iron give exceptionally good results.

Oarbon-Toolr Steei. Regular carbon-tool steel when used for
draw broaches should ordinarily contain from 1.0 ta 1.1 per cent
carbon, although excellent results follow the use of steel containing
1.25 per cent carbon, if the pull b not too great; in the latter case»
the lower carbon content b to be preferred.

Open' Hearth Steel. For broaches that are not to be subjected'
to great pulling strain, a good grade of basic open-hiearth steel
containing thirty points, carbon works well, especially where the
broaching is done directly from a cored or forged hole and where
the broach is to be subjected to considerable vibration* Broachea
made from thb material must be pack hardened.

Making Draw Broaches. Cutting and Turning to Sim, No
general method can be given for making all forms of draw biVMiehes,
as the desirable method depends on the form of the finished tool
If the broach is to be used for producing square, hexagonal, or other
holes, with round corners, from a round drilled hole, select steel
adapted to the individual job. Cut the steel to length, then
center and square the ends; after which it should be rough-turned
and the shank turned to finish size, which is generally the size of the

TOOL-MAKING

24d

drilled hole. However, if the end of the shank is to fit some holding
device that goes with the machine, then that portion must be turned
to that size as shown in Fig. 400. This, of course, must not be
larger than the drilled hole.

The balance of the piece should now be turned to the largest
diameter of the broach plus a small amount for finish, and tapered

Fig. 400. Typical Puli Broaoh Showinc Method of Holdioc End
Courtesy c/J. N. LapoinU Company, New London, Connecticut

from the teeth nearest the fastened end to within four teeth of the
opposite end; this end should be straight in order that the last
four teeth may all "be of a size to allow for wear. Fig, 390. Having
the four teeth of finish size insures correct sizing of holes, even after
the cutting teeth have been sharpened several times.

Annealing, Many tool-makers who make a specialty of broach-
ing tools always anneal the broach after the teeth have been blocked
out. After annealing, the teeth are cut to depth and the broach
finished and hardened.

Cutting Teeth. If the broach is to produce a square hole with
round corners. Fig. 394, the teeth may be first produced on the
lathe on the round piece.
Fig. 391, with a tool that spac^juock^

will produce a cut of the

desired form and depth. The

spacing can be obtained by

means of the lead screw, or,

with a spacing block and

damp with a set screw. Fig.

401. The clamp should be

attached to the bed of the

lathe and the screw set

against the space block as shown. The block, the thickness of which

corresponds with the desired pitch of the teeth, is removed, and

the carriage moved along against the screw. In this way, the

Fig. 401. Spacing Biocic and Clamp

290 TOOL-MAKING

teeth are spaced exactly alike for the entire length of the cutting
portion of the broach.

Before the broach is removed from the lathe, the tops of the
teeth -should be backed off for clearance, as shown at c. Fig. 391,
by means of a flat-nosed tool. After all the teeth have been backed
off, the broach should he placed between the index centers of the
milling machine, and one center raised or the other lowered to the
taptr of the brpach and the flats milled. The large end — that Is,
the last four teeth — should be milled to the desired dimensions
parallel to the axis.

The teeth on the flat portions may now be produced by milling
or planing, to correspond in shape and depth to those on the round
corners.

Filing Teeth. It is necessary to have the face and the back of
the tooth smooth in order that chips will be cleared readily. This
can be secured by filing, and should be done before the top surfaces
that make the clearance angle are fileH. Previous to filing the sur-
faces of the clearance angle, apply copperas in order that the work-
man may see where he is filing. File to the cutting edge, but do
not remove Any stock from the edge, because if one tooth is made
short, the next tooth must do double duty. As previously stated,
thr four teeth at the large end of the broach should be of equal
diameter if the tool is to hold its size.

Piich of Teeth. The pitch of broach teeth cannot be stated
arbitrarily/ for the distance from one tooth to the next depends
in a great measure on the amount of stock to he removed, the length
of the broach, and the thickness of the piece to be broached. The
following formula, however, is used by some manufacturers of
broaches for use under average conditions:

P=Vrx0.35

where P« pitch, or distance apart of teeth; and 1 = length of hole
to be broached. For example, if a broach is to be made for broach-
ing a hole 4 inches long, the distance between the teeth would equal
2x0.35, or .7 inch, approximately. In the case of a broach of large
diameter, it is possible to cut the teeth deep and a little closer together
than if the broach were of smaller diameter, as in the latter case the
teeth must be shallower to give strength to the broach. It is always

TOOL-MAKING 251

necessary to design the broach with the teeth so spaced and of such
depth that the space between them w^iil hold the chips removed,
for otherwise the chips would wedge themselves between the broach
-and the walls of the hole, thus tearing the surface of the walls, and
in all probability breaking the broach.

Size of Teeth, The variation of size of adjoining teeth cannot
be stated arbitrarily, Under average conditions, an increase in
size of from .001 to .003 inch works well on steel, and from .002 to
.004 inch on cast iron or brass. Yet working conditions and the
character of the material make it possible and advisable to change
these amounts of increase in size at times.

If the broach has long cutting teeth, it is advisable tq nick
them to break the chip, as the long chip, especially if it is steel,
would be likely to cause trouble. When nicking the teeth, make
sure that no two adjoining teeth have their nicks in line.

Angle of Teeth. The face /, Fig. 3^1, of the teeth of broaches
is many times made at right angles to* the axis of the broach. A
tooth cut as shown at a,
however, will require less
force to pull it through
the work if made at an
angle, yet under ordinary
conditions the shape /

shown at h is considered Fig. 402. DiAgram showing Angle of Broach T««th

the better one.

The clearance angle, c, is generally about 2 degrees, although
at times but 1 degree is given.

The teeth of broaches are sometimes made at an angle, as shown
in Fig. 402. In the case of square and rectangular broaches, teeth
on opposite sides are made at opposite angles in order to balance

the out.

Hardening, When hardening broaches, it is necessary to heat
them uniformly their entire length, a process best carried on in an
oven furnace or in a piece of pipe in an ordinary furnace. In order
to get a uniform temperature, the piece should be turned frequently.
When it has become uniformly .Seated to the proper temperature,
plunge it vertically in a bath of warm, not hot,- water in which a
quantity of salt has been dissolved, and work up and down until

252 TOOL-MAKING

cooled to the temperature of the water, when the broich may be
removed and tested for straightness. If it has sprung in the opera-
tion of hardening, it may be strai)[htened in the following maaner:
Place the broach in a screw press or a drill-press table on two
blocks of hard wood, then, with a spirit lamp or bunsen burner,
heat it until lard oil on the surface smokes; now,
with a third block of wood between the work
and spindle of machine, apply pressure by means
of the spinale until tlte tool is straiiflitened It
will be necessary to do all the straighten in);
before the temperature drops much, or the broach
will break. After the straightening, the temper
may be drawn. Some hardeners, who are quite
skilful in this particular line of work, straighten
and draw the temper at one operation. Broaches
made from oil-hardening steels are heated as
described above and hardened in oil. Broaches
made from low-carbon open-hearth steel are
packed in charred leather in a piece of gas pipe,
the ends of which are sealed, and the whole sub-
jected to a red heat for several hours, the time
depending on the size of the piece. When the
carbon has penetrated to the desired depth, the
broach is removed from the pipe and plunged
vertically into a bath of hardening oil; or, if a
harder effect is desired, into a bath of lukewarm

After hardening, (he broach should be tested
for straightness; if it has sprung, it should be
heated and straightened, as previously described,
Ri ""gl^f};"' '"^ «"d the temper drawn to a light straw color

Loi^ Broach vs. Short Broach. Generally
speaking, the length of a broach depends on the amount of stock to
be cut out of the hole, and the capacity of the machine. Some
broach-makers, however, believe it is economy to use several short
broaches instead of one tong.broach, even where the capacity of the
machine makes it possible to use a long one, maintaining that long
broaches are more costly to make, and more likely to break when

TOOL-MAKING

253

in use. The advisability of either depends on so many factors that
are peculiar to the individual shop, that it is not possible to make
any general statement that will fit all cases.

Push Broaches. Broaches of the form shown in Fig. 403, are
called push broaches, and are used in special presses having an
adjustable stroke of from 1} to 12 inches. It is generally necessary
to use several broaches in finishing a hole, especially if they are short.
At times it is desirable to use a long broach in a press having a
comparatively short stroke. This may be accomplished by ushig
blocks. First drive the broach into the work as far as possible
with the stroke of the press; then, wlien the ram is at the top of the
stroke, insert a block the thickness of which is equal to the stroke of

(P) (b) (^

Fig. 404. Progressive PunchiDgs «f KeyseatiDg Mschine

the press between the ram and the top of the broach. At each
successive stroke of the press, use a thicker block.

When broaches are used in a press, it is always advisable to use
a driver having a V-shaped opening in face.

Keyseating Machine. For many jobs a keyseating machine
is an absolutely essential part of the equipment. Where work is
done in small lots, it is frequently advisable to use this machine
instead of a broaching machine, as the cost of cutting tools is but a
fraction of the cost of a broach.

At times this machine is used to remove a portion of the stock
before broaching, as is the case with the piece shown in Fig. 404.
A hole is drilled in the piece, as shown at a; the piece is then placed
in the keyseating machine and the hole cut to the form shown

2H TOOL.MAKING

at b, aiiet which it may be brought to £nUh size snd shape e by
broaching.

Irregularly shaped holes that are larger at one end than at
the other, as shown in the circular piece, Fig. A(&, are easily

machined in a keyseating machine by the use of properly shaped
cutting tools and rightly designed holding fixtures.

DROP-FOROINO DIES
It is extremely difficult, as well as very costly, to produce
many forgings by hand, if it is necessary that they be of uniform size
and form. As tite tendency in all up-to-date sht^ is to produce

TOOL-MAKING

duplicate «rorlc, and
many parti are tuined
out by f orgjng, dies are
made which have the
shape of the piece to be
forged cut into t^ faces.
A forging of the desired
mse attd dbape is pnn
duced by fordng the
heated metal into the
impres^ons.

Drop>Foiffaif Pn>c>
oa. In forging, the dies
may t>e held in forging
machines of varioua
kinds, such as iheforginf
pretf, the buUdoger, ibe
drop pm* (where the ram
is raised by means of rdls
acting on a board at-
tached to the ram or
head), or the tteam dtop.
Pig. 406. Although the
board drop. Pig. 407, u
tite form most commonly
used, it is pving way in
many places to the steam
drop on account of the
more positive and speedy
action. It is frequently
necessary to use several
Bets of dies, or several
Bets of impressions in the
same dies; jfrat, a break-
bg~down impression;
itamd, a roughing im-
pression, and tkird, a
finish impression.

8M TOOL-MAKING

Considerable experience, coupled with good judgment,
Tcquirad to lay off properly a breaking-down impresaion in

■Uh Ctmrmn. BntttfK W'

foiging die, in Ontor that the material may be rightly distributed
w> u to fill the other impressions without cKcesMve w^ste of st^ck.

TOOL-MAKING 257

A die-maker with limited experience in laying out dies should give
special attention to the laying out of breaking-down impressions in
order that he may be able to do this kind of work in a satisfactory
manner. _

After forging, a quantity of surplus »tock will show around
the desired blank; this is called the Jlaah. The flash is removed
by forcing the forging through a trimming die. The impression in
the trimming die is the exact shape of the forging, and the forging
passing through has the flash cut away. Large forgings are trimmed
while red hot, and the operation is known as hot trimming, while
small forgings are generally trimmed cold, and the process is called
cold trimming.

Making Drop-Forging Dies. Stoclc, Drop-forging dies are made
from crucible steel which is furnished in the form of die blocks
in any desired size; or, as is the case in many shops, they are made
from open-hearth steel, in which case they are procured from the
mill in pieces of the proper size, or the stock is purchased in bars
and cut up and forged to size as wanted. The latter method proves
satisfactory where the equipment of the shop allows the heating
and handling of pieces of metal weighing several tons. As it is then
possible to cut off, forge, and anneal pieces of almost any size, there
is very little waste.

Small dies are generally hardened, while large dies seldom are.
Large dies that are not to be hardened are often made from steel
containing a proportion of nickel, or other alloy that insures desired
ability to stand up,when in use.

Cutting. Most die blocks are planed to size after annealing,
although in some shops they are milled to size. The tang is produced
by either planing or milling, according to the equipment of the shop.
The impressions are carefully laid out on the faces of the dies by
means of templets, and the metal cut away with milling machine
cutters, the work being done in a die-sinking machine. The cutters
are made of a' taper that produces the proper draft in the die. ,It
is necessary to give the impression sufficient draft so that the forging
will not stick in the die. The draft which should be used varies
from 3 to 5 degrees. _

As it is not possible to get into corners with milling cutters, it
is frequently necessary to remove some of the stock with a cold

25S

TOOL-MAKING

cfaiseli scraper, and files. Die-sinkers use a special type of file in
working the walls of the impressions; these are of various forms
and are bent to allow of use in the impressions. They are called
rifflera. In Fig. 408 are shown various special forms of files and rasps.
Coating^ Lead. Aft%r the impressions in the die are finished
to size and shape, the dies are clamped face to face, and lead is poured

7?f/f££ >S^(/AR£ BASTATiD

Hand 3a^tard

Fiat Float ^Safz 3/dje

Halt JRound Bastard

Thphz >5^(/An£ T^A^p

Found Ra6p

Fig 408 Special Forms of File > and Rasp*

into the impressions. The resulting piece, known as the lead, is
measured, and, if found correct, is marked and laid away for refer
ence. In some shops the die faces are blocked apart when the lead
is cast. After casting, the blocking is removed, the dies are placed
in a hydraulic press, and the lead is forced out into all parts of the
die; if a flash is thrown out between the dies, this may b« cut away
Imd the lead pressed again. As a rule^ the pressing of a lead is not

TOOL-MAKING 259

tlie practiM, as it is necessary to allow for ahrinkage and this involves
the use of tables of coefficients of expansion of metals.

If the lead, when measured, is found not to be of the dedred
die, aufiicient stock may be removed to give desired results, and
another lead cast.

For many dies, it will be found necessary to cut away the faces
of the dies around the impressions, Fig. 40S, to provide a place for
the flash, in order that it may not lie between the dies, and so produce
forgings of varying thickness,

SlMnping Identifieation Marks. When the die blocks are
finished, and before they are hardened, the name of the piece to be
forged in the die. as well as the shelf
numberofthedie, should be stamped
on one or botli ends of each. While
this might not seem necessary in the
shop having only ten or twelve seta
of dies, it w necessary in the shop
having hundreds, some of which are
seldom used. If the^ dies are kept
in a certain place on certun shelves,
and a record ia kept of the dies and
the shelves, it is an easy matter to
find any die, at any time.

Hardening. When hardening
drop-forging dies, it is necessary to Rf.wa. tHrwiiifaixiCutAnro
onploy some form of heating furnace

that will insure heats of the proper temperature — in other words, a
furnace that can be easily and quickly regulated. The die should
be heated rapidly, yet not faster than is condstent with uniform
heating, or the comers and light sections will be overheated and
weakened.

If large pieces of steel are placed in a furnace and allowed to
remain exposed to the direct heat and to any air that may be in the
furnace, their surfaces are likely to become, decarbonized. As the
faces and walls of the impressions of forging dies must be hardened,
it is deidrable to protect them. This is sometimes done by placing
a quantity of granulated charcoal in the furnace on the hearth, and
laying the face of the die on this. A more satisfactory method

yea tool-making

consists in ]Jadng one or two inches ot granntated chnrm) leathei

in the bottom ot a shallow hardening box, laying the face of ihe die

OQ the leather, then filling the box with leather, as shown in Fig. 410

The die may then remain in

the furnace imtil it b uni-

fonoly heated throughout.

To prevent unequnl heating

in the comers at base of the

tang, the eornera are filled

with fire clBy,B3shown at a.

rit.410. HuifeniivB^miiiiMetDCiiund Tlie form of bath de-

^^^^' pends somewhat, of course,

on the character of the pieces to be hardcneil. One form that is

satisfactory for most work ot this kind, has the die resting upon the

supporting wires. Fig. 411. 1'lie overflow pipe should be telescoped,

thus enabling the operator to regulate the depth of watcrin the tank.

To prevent the tang from becoming distorted, it is advisable to

quench this portion first; this is accomplished by placing the die,

tang down, on the wires, and allowing the stream of water from

the supply pipe to play

against tlie tang. The

die should be left in this

position until the tang

is cooled below a red,

when the die should be

turned to bring the Face

down, and tlie supply

stream allowed to play

against this portion until

it is hardened.

To prevent the tang
from softening before the
tit 111, Foim^oi Haiden^jBiiii wiUi Die oa face bccomes hard, tum

water, by meana of a
dipper, on to the tang until the red has disappeared from the face;
then cease pouring on to the tang and allow the heat to work from
the center of the block up through the tang, which will in all proba-
bility be reheated to a low red.

TOOL-MAKING

261

After the block has cooled, it should b^ plaeed over a fire and
heated to remove hardening strains. While heating, the surface
may be brightened and the heat continued until the temper is
drawn the desired amoUnt.

At times it b necessary to harden a die having slender projections
or some weak portion which is likely to crack during the process.
Cracking results from the unequal contraction of the various parts,
and can be avoided by rubbing soap on the projection, especially
where it joins the die; or, by means of an oil can, a little lard or
sperm oil may be applied to these parts. This should be done after
the die is red hot, and just before it is placed in the bath. If the

I •

Bottom View
Fie. 412. Hobbing Drop-Forgiiig Dies. A— Piece to be forged; ^— Hob

tang is quenched first, the oil may be applied just before the die is
turned to harden the face.

Mobbing Drop-Forging Dies. It b the custom in some shops
to produce the impression in the face of forging dies with a male die,
or hob, as it is called. A hob is made of the same general shape
as one-half of the piece to be forged, but exactly opposite the
shape of the impression desired in one die. Another hob is made
the shape of which is the opposite of the impression desired
in the other blank.

Making Impression, Fig. 412 shows a piece to be forged, A,
and a hob, B. The hob has a shank that fits a holder in the ram

262 TOOL-MAKING

of the drop hammer. The hobs are hardened before using, and
after hardening, one of them is placed in the holder in the ram;
the die block is heated to a good forging heat and securely fastened
to the anvil of the drop, and the hob is driven into the face of the
die. This operation is repeated until the impression is considerably
deeper than that desired when finished. This is necessary as the
top surface of the die must be cut away to remove the rounded
portion at the top of the impression, occasioned by the stock drawing
away in the bobbing.

Cleaning and Smooihin>g Impression. After driving the hob
to the required depth, the block is reheated and annealed. When
the block has cooled, the scale on the surface of the walls of the
impression is removed by filling the impression with a solution of
sulphtiric acid and water — one part acid, and two parts water.
After the scale has been removed, the acid should be turned out
and the surface well washed, first with hot water, then with a strong
solution of potash, and then, once more, with water. The surface,
when dry, should be oiled to prevent rusting.

Cold- Dropping Impression. The walls of the impression may
now be finished smooth with scrapers and files. After the surfaces
are finished, it is the custom in some shops to cold-drop the impres-
sion, that is, to place the die in the drop hammer again and drop
the hob into the impression while the steel is cold. This custom,
however, is not generally observed. After finishing, the dies are
hardened in the usual manner.

Preventing Oxidation. A saving in labor may be effected, if,
when the die is heated for annealing, the impression is filled with
fire clay mixed with water to the consistency of dough. The fire
clay prevents the air coming in contact with the steel, and does
away, to a great extent, with oxidation.

Cold-Striking Dies. Many times pieces are forged which cannot
he brought near enough to desired size by hammering when hot;
or which must be much stiffer than hot-forging would leave them.
In such cases cold-dropping or cold-striking, as it is sometimes
called, must be resorted to.

After the pieces are hot-forged to a size slightly larger than
finish, and the flash is trimmed away, they are pickled to remove
the scale incident to the high forging heats. After pickling, and

TOOL-MAKING 263

when they are cold, they are again taken to the drop hammer and
given one or more blows, in died known as cold-striking dies.

The impression in a cold-striking die is made of the desired
size of the finish piece, as no allowance need be made for contraction
of the metal as is necessary when hot-forging. Since there is much
greater strain on a cold-striking die than on one used for hot-forging,
it is necessary to harden the former much deeper than the latter
to prevent sinking when the die is used. For this reason, the dies
should be made from steel having a comparatively high-carbon
content.

While a large percentage of dies used for hot-forging are made
from open-hearth steel, those used for cold-dropping are made from
crucible tool steel. In many forging plants, this class of die is made
from alloy steel prepared specially for this purpose; in such cases
the heat treatment may be somewhat different from that given
similar dies made from crucible tool steel. As the treatment varies
for steels of different makes, it is necessary to follow the instruc-
tions furnished with the steel.

GAGES

Gages are used in machine shops to make one part of a machine,
apparatus, or tool correspond with some other part, so that when
the whole is assembled, every part will go in its place with little
or no fitting.

In shops where work is made on the interchangeable plan —
that is, where a piece of work made today will exactly duplicate a
similar piece made at some time in the past — a very thorough system
of inspection' is necessary. In order that the inspection may accom-
plish the desired result, gages are made that show any variation
of the pieces from a given standard. There are several forms of
gages designed for various classes of work, but only those in common
use in the general machine shop will be considered here.

General Directions for Making Gages. Gages are generally
made of tool steel; but hardened steel has a tendency to change its
size or shape for a considerable time after the hardening has
occurred. This change is ascribed by acknowledged authorities to
a rearrangement of the minute particles or molecules of the steel,
whose original arrangement had beeji changed by the process of

264 TOOL-MAKING

hardening. While this change of size or shape is small, so small,
indeed, that it need not be considered, except in the case of gages
where great accuracy is required, yet it has led some manufac-
turers to use machine steel.

If tool steel is used, the tendency to change shape may be
overcome to some extent by grinding the gage to within a few
thousandths of an inch of finish size, and allowing it to "season'*
as it is terme(f among mechanics; that is, it is laid aside for a few
months or a year, before being finished to size. This method Is,
of course, open to serious objection if the gage is needed for
immediate use.

To save time, it is customary in many shops to draw the temper
to a straw color, allowing the gage to cool slowly and repeating the
operation several times. It is necessary to brighten the steel each
time before drawing, the temper in order that the colors may be
readily seen; as this has a softening effect, the gage will not last so
long as if left hard.

AccMraoy Regtwred. When making gages the workman should
observe the points emphasized with regard to "approximate and
precise measurements" in the first pages of this book. While
gage-making is generally considered very accurate work, unnecessary
accuracy should not be used. If a gage is intended for work where
a variation of .005 inch is permissible, it is folly and a waste of
time to attempt to make it within a limit of variation of .0001 inch.
On the other hand, if the gage is to be used as a test gage on work
requiring great exactness, it is necessary to use every possible effort
to attain that end.

If a gage is to be made of tool steel, it is necessary first to remove
all the outside portion (skin) of the stock, and block the gage out some-
where near to shape; it should then be thoroughly annealed. If the
gage is flat and should spring while annealing, it should rijot be
straightened cold, as it would be almost sure to spring when hardened.

It is necessary to stamp the name of tlie part to be gaged and
the sizes of the different parts of the gage. The workman should
bear in mind that the effect of driving stamps, letters, or figures into
a piece of steel will be to stretch it; consequently, it is advisable to
stamp the gage before finishing any of the gaging portions to size,
even if there is an allowance for grinding.

TOOL-MAKING

266

Plug Gages. Plug gages are those used to measure the size
of a hole.

To make the plug gage shown ia Fig. 413, stock should be
selected, enough larger than finish size to allow for turning off the
decarbonized surface. After roughing out. the handle B should be
turned to size and knurled, the portion C should be turned to size
and finished, and the spot in the center of the handle should be
milled. The size of the gage and any distinguishing mark or name
of the article to be gaged may l)e stamped at B^ as shown, or, as
is the custom in many shops, it may be done at C. After stamping,
the gage end A may be turned to a size .010 or .015 inch larger than
finish, to allow for grinding. Plug gages should be heated very
carefully for hardening, as the lower the heat, the more compact
will be the grain;, and a piece of steel whose grain is fine and com-
pact will wear better than one whose grain is coarse. If the gage
is one requiring great
accuracy, it may be left ^— m^^i^— . o
.0025 or .003 inch above
size and allowed to sea-
son, provided this pre-
caution is deemed neces-
sary; if not, the gage
may be ground to a size .001 inch larger than finish, after which it
must be lapped to finish size.

Cajtehardening Machine^ieel Gages. When plug gages are
made of machine steel, they should be casehardened in the following
manner: They may be packed as for pack hardening, that is,
in charred leather. They should run in the furnace for seven or
eight hours after they are red hot. The box should then be taken
from the furnace and allowed to cool, after which the gage, enclosed
in a piece of tube, may be heated in an ordinary fire. When it
reaches a low red heat, it should be plunged into a bath of raw
linseed oil. It will not be necessary ta draw the temper, and the
danger of alteration as it ages is done away with.

The reason for not hardening when the gage has run the required
length of time in the furnace, is that the efl^ect of the second heat
is to refine the steel, making the grain more compact, like properly
hardened tool steel, thus increasing its wearing qualities.

Viz. 413. Typical Plug Gage

266

TOOL-MAKING

Grinding. When grinding a gage of this description, it os
advisable to use a grinding niiachine haxing a supply of water running
on the work to keep it cool, but if this form of grinder is not available,
the gage should not be heated any more than is necessary. It
should be measured while cool; as steel always expands from the
Bctioki of heat, and if ground to size when heated, would be too
small after cooling.

If possible, a form of grinder having two dead centers should
be used — that is, one in which neither genter revolves. This is
mentioned on account of the tendency in some shops where there
is no universal grinder, and an engine lathe is to be used as a grinder,
to select the poorest lathe in the shop for the purpose. Lathes
that have been in use for some time are very likely to have become
worn, so that accurate work is impossible; this is. especially true

Fig. 414. Good Form of Lap for Cylihdrical Suriaces

of the head spindle, which will duplicate its own inaccuracy on the
piece being ground.

If obliged to do the work on a machine of this description, it is
advisable to leave a trifle more stock for lapping than if a suitable
grinder is used. A. coarse wheel free from glaze should be employed
to grind within .004 of finish size, after which a finer wheel may be
substituted to grind to lapping size.

lAipping. A very simple method of making a lap for use on
a cylindrical surface is shown in Fig. 414; this consists of a piece of
cast iron having a hole bored a trifle .larger than the size of the
^acge to be ground. It is split as shown, and closed by means of
the screw A.

If there is much gage or other work requiring lapping, it is
advisable to make a lap as shown in Fig. 415. The holder A has a

TOOL-MAKING

267

hole bored to receive the laps, which are made in the form of ringsi
split in three places, which fit the holder. One cut is carried through
one wall; while the other two, commencing at the inside, terminate

Fig. 4lS. Lap for Cages

a little distance from the outside surface. The laps may be held in
place by means of the pointed screw shown at B.

The lapping should be done with flour emery mixed whh oil.
This operation has the effect of heating the gage to a degree that
would make it unsafe to caliper, and on this account it is necessary
to have a dish of water handy in which to cool the gage before
measuring it. This water should not be cMt or incorrect meas-
urements will result; it should be as nearly as possible the average
temperature of the room in which it is to be used, about 70 degrees.

Grinding Off End. After the tool has been lapped to the required
size, it may be placed in a chuck on the grinding machine and the
end ground off to remove any portion that is slightly Smaller than
the rest of the gage, as the lapping is likely to grind the extreme
end slightly tapering. In order to save time when grinding the end,

Fig. 416. Lap with Cupped End Which Is Later Ground Off

the gage may be made as shown in Fig. .416. ^he se^^tional viiew
shows the end cupped in, leaving a wall i^ inch to } inch thick,
according to the si^e of the gage, the larger sizes having the thicker

268 TOOL-MAKING

walb; the cupping should be Bbout iV inch deep and the corner
left slightly rounded, as shown.

Another method is to cut a groove with a round-nostd cutling-off

tool, leaving a disc on the end. Fig. 417. It the gage has its end

shaped as in Fig. 41C,

the projectiiig portion,

I, is ground away

I until the end of the gage

: straight ucross. In

cose the gage is made as

-o«r.adc™jmtiv.M shown in Fig. 417, the

disc A is broken off and the end ground as described.

Ring Oages. Rinff gages are intended for use on O'tindrical
pieces of work. Those which are smaller than one inch in diameter
are generally made of a solid piece of tool steel, or machine steel
which is casehardened. For a giige one inch or larger, custom
varies, some tool-makers making it of a solid piece, while others
make the body of cast iron or machine steel, into which is forced
a hardened steel bushing \shich is the gage proper

Boring Holet It is advisable when making a solid gage
to use a piece of steel somewhat longer than finish duncnsions as
shown in Fig 411 the dimension ( npristntrng the finish kngth

oF gage, and the projections BB being left until the gage is lapped
to size. The hole should be bored somewhat smaller than the
finish swe, in order to allow for grinding and lapping. If a grinder
having an internal grinding attachment is not available, the allow-

TOOL-MAKING

269

ance should be much less thau if it were possible to grind the walls
of the hole. If the gage is to be ground to size, an allowance of .005
inch will be about the proper amount; if not to be ground and the
hole is bored straight and smooth, an allowance of from -.OOIS to
.002 inch should be made; but the amount left cannot be given
arbitrarily, as much depends on the condition of the hole and
the care used in hardening.

Hardening. After the hole has been bored, the blank may
be placed on a mandrel, the ends, shaped as shown in Fig. 418, ](Ji9
outside diameter turned and knurled, and the portion C necked
to the bottom of the knurling. The size and any distinguishing
marks may be stamped on this necked portion as shown. The
l^ge is now ready for hardening, . and much the best results are
obtained^''fn>m~pack''.hapxlening. If this method cannot be used,
the gage should be carefully heated in a muffle furnace or in a piece

Fig. 419. liCad Ld^p on Mandrel

of gas pipe or iron tube in an ordinary fire. When it reaches a low
uniform heat, it should be plunged into a bath of brine and worked
around so that the bath may circulate freely through the holes.
Excellent results follow if a bath is used having a jet of brine or
water coming up from the bottom and passing through the hole
with some force, in order to remove any steam that may be generated.

Grinding. If it is considered necessary to allow the gage to
season, the bole may be ground enough to remove part of the allow-
ance, and the gage laid away< If it is not considered necessary to
do this, it may be ground .001 or .0015 inch smaller than finish size
to allow for^ lapping.

Lapping, When lapping a' ring gage to size, it is necessary
to use a good lap. A poor lap is the cause of many of the failures
when attempting to do satisfactory work of this description.

When a grinder with an internal grinding attachment is not
available, and it is found necessary to lekve considerable stock in the
hold for lapping, many tool-makers claim best results from using two

270

TOOL-MAKING

laps — ^the first, aiciK^ tap, for removing most of the stock, and the
second, a bast-iron lap^ for finishing the hole to size. In either
case, the lap should be in {he form of a shell which should be held
on a tepfM* mandrel when in use. Fig. 419 shows a lead lap on a
'inandrel'as described.

The. mandrel should be made with the ends somewhat smaller
than the body, which should be tapering, in order that the lap may
be expanded as it is driven on. A groove is cut the entire length
of the body with a convex milling cutter, or it may be cut in the
shaper or planer, holding the mandrel between centers, or in the

vise, cutting the slot with a round-nosed
tool. A mold for casting the lead to
shape may be idade of two pieces of wood
an inch or two longer than the desired
length of lap, which itself should be throe
times the length of the hole in the gage.
The two pieces of wood should be
clamped toother, and the hole bored
with'^a bit about \ inch larger than the
diameter of the finished lap; after boring
to'the required depth, a bit should then
be used the size of the projection on the
small end of the mandrel. The hole bored
with this bit should be a trifle deeper than
the length of the projection. After the
hole has been bored in the mold, as
described, the mandrel may Bib put in
position. Fig. 420, with the mold vertical.
Two narrow strips of wood or metal are placed on top of the mold
to hold the mandrel central and the lead is poured. In order that
the lead may run well, it will be necessary to heat the mandrel
somewhat; this should be done befqre putting it in the mold. After
the lead has become cool, the mold may be opened, and the casting
removed. It should be, placed in the lathe on the mandrel, and
turned to a size .001 inch smaller than the hole in the gage; it
may then be charged with fine «emery and oil.

For finishing the hole to size, or lapping a hok ground nearly
to size, it is advisable to use a lap made of harder material than lead;

Fif. 420. Mandrel in Mold

TOOL-MAKING

271

for this purpose fine-grained cast iron answers admirably, a though
copper is preferred by some. In order to make a cast-iron lap,
a mandrel is necessary, with a taper from | to ^ ihch per foot of
length. The slight taper is used in order that the lap may not
increase its size too rapidly when driven on the mandrel. The cast-,
iron lap (sleeve) should be bored with a taper corresponding to the
taper of the mandrel, after which it may be forced on the mandrel
and turned to size and split as shown in Fig. 421. One slot should
extend through the' wall as shown at A, while the other. two slots
BB extend deep enough to allow the lap to expand readily. ■ Before
finishing the hole to size, the lap shoiild be forced a trifle farther
on the mandrel, and trued in the grinder, an eodery wheel being

1 ' ' ? '

. ^ y

Fig. 4;21. Lap Forced oa Mandrel and Split

used to cut the lap. The lap should be perfectly rouQd and straight,
in order to produce true holes. For the finish lapping,, ihe finest
of flour emery should he used.

Finishing Gage. The same precautions should be observed
while cooling the gage, before trying ike size of hole, as were noted
for plug gages. In order to clean the gage of the oil and emery,
it should be dipped in a can of benzine, which readily reiAoves
any dirt. Extreme care must be exercised when washing work in
benzine, that it is not brought into the vicinity of a flame of any kind,
as 'benzine is extremely- infTammable, and very -difficult to extinguish
if it becomes ignited; should it become ignited, it can be extinguished
with a piece of heavy sacking.

The ring should be fitted to the plug gage whicl) has previously
been finished to the correct size. It must be borne, in mind that the
temperature of the plug and ring should be as nearly as possible
the same when tested.

Snap Qage. This form of gage is used more extensively than
any^ other for oiitside measurements. It is extremely useful
in gaging a dimension between two shoulders as ^hown at A,

272

TOOL-MAKING

Figs. 422 and 423; in the former case, the piece being machined
is Hat» while in the latter it is cylindrical.

A snap gage may be designed to meet the requirements of the
particular piece of work. >yhen it is intended for use on a cylindrical
piece, the opening should be made a trifle deeper than one-half

Pif . 422. Fl»t Piece Easily Gaged
with Snap Gage

Fig. 423. Cylindneal Piece Adapted to Ui
oi Snap Gage

the diameter of the piece to be measured, when it is intended for
flat work, the depth of the slot depends on the nature of the work.
Snap Gages for Cylindrical Work. A gage of this type is shown
in Fig. 424, A representing the cylindrical piece to be gaged. When
making this gage, the stock should be blocked out somewhat near
to shape and annealed; after annealing, the sides may be made
flat and parallel; and the size and any distinguishing marks stamped
as shown; the gage part may then be worked to a size from .008
to .010 inch smaller than finish, to allow for grinding. The outer
edges should be rounded somewhat jto prevent cutting the hands of
the operator.

Some tool-makers harden only the prongs that come in contact
with the work, while others harden the entire tool. If the contact

points alone are to be hardened, the heating
can best be done in a crucible of red-hot
lead; if this is not at hand, pieces of flat
iron may be placed, one on each side of the
gage, allowing the ends to be hardened to
project bevond the pieces; the whole may
now be grasped in a pair of tongs and placed
in the Are. The points will reach a harden-,
ing heat before the portion between the flat
pieces is much afl'ected . The gage may be plunged in water or brine to
harden. If it is considered advisable to harden the gage all over,
it should be heated very carefully in the fire, so that the blast
does not strike it, and turned frequently to insure a uniform heat.
When it reaches a low red heat, remove it from the fire and plunge

Fig. 424. Snap Gage

TOOL-MAKING

i73

Itmfhrenem

Fif . 425. Mal« Gafe

it into the bath. If the gage is quite thin, a bath of oil will harden
it sufficiently; if it ia dipped in water or brine, the bath should be
warmed somewhat in order to avoid, as much as possible, any
tendency to spring.

After hardening, the gage is ground to size .0006 inch smaller
than finish and lapped to size; the method used in grinding gages
of this character will be
described later.

MaU Gages for Test-
ing Snap Ga§es, In order
to be able to give gages
the correct size, it is
often necessary to make male gages, the simplest form of which is
shown in Fig. 425. It is a flat piece of tool steel; made slightly
small on one end to avoid grinding to size the entire length. After
the Urge end has been hardened, it is ground to size and the gage
is then ready for use in testing the size of the female ^nap gages
while the latter are being lapped to size, or when being ground, if
lapping is not considered necessary. When it is necessary to make
a snap gage for measuring two or more dimensions on a piece of
work, it may be made as shown in Fig. 426t Fig. 427 represents the
piece to be gaged.

After cutting off the steel for the gage, the sides should be planed
to remove the skin. One of the flat surfaces may be colored either

O MICTION BUXK

^TrTVV

<£

Fie. 426. Snap Gac« Givinf Several MeMurfmeaU

with blue vitriol or by holding it over a fire until the surface becomes
blue. The handle and the openings that constitute the gages can
then be laid off on the surface. After milling the handle to shape,
the holes shown at the corners of the Openings may be drilled. These '
holes facilitate the operations of filing and grinding, particularly
the latter. The openings may be milled or planed to a size about

274

TOOL-MAKING

«>

•

■ ^^

— '

Fig. 427. Friction Block

^ inch smaller than finish, and the gage is ready for annealing,
after which the two flat surfaces may be planed or filed until flat
and parallel. The name of the piece to be gaged and the size of
the openings may be stamped as shown. If the tool is intended

for gaging work where a few
thousandths of an inch either way
would make no particular differ-
ence, it is customary to make the
openings to the given sizes before
the gage is hardened. However,
if the gage must be exact to size, it
is necessary to leave from .003 to
.005 inch on each measuring surface, to allow for grinding. If it
is desirable to have the gage retain its.exact size for any considerable
length of time, it will be found necessary to finish it to size by lappuig
after it is ground.

Grinding Snap Gages. A snap gage may be held in a vise on
the universal grinder when the openings are ground to size, provided
it is held in such a way that it cannot spring. If sprung in any man-
ner while being held, it would assume its normal shape when taken
from the vise, and consequently the measuring surfaces would not

beparallel. Asthbwould
destroy its accuracy, it
is highly important that
the measuring surfaces
of the openings be par-
allel.

A snap gage may be
clamped to an angle iron
held in the vise while
grinding, Fig. 428, or it
may be clamped to a
piece of machine steel
or cast iron centered,
Fig. 429. This holder should be placed between the centers of the
grinding machine.

If the opening whose gaging surfaces are to be ground is of
sufficient width, an emery wheel of the form shown in Fig. 430 may

Fig. 428. Snap Gage Clamped in Viae for Grindiog

TOOL-MAKING

275

be used; or a wheel may be recessed on its sides as shown in Fig. 431 .
If the wheel is of the form shown in Fig. 430, it will be necessary

Fif . 429. Snap Gaxc Clamped to Centcred«Pieoe

to remove it after grinding one wall of the opening and to reverse

it to grind the other. If, however, the oi)ening is too narrow to allow

this type of wheel, a very thin wheel may

be made to answer the purpose, but it

will be necessary to swivel the head of

the grinder a little, in order that the

wheel may touch the surface to be ground

only at the corner of the wheel. An

engine lathe or a bench lathe can be

substitute<l if a grinding machine is not

available. If the lathe is provided with

a grinding attachment, the holder to

which the gage is attached maybe placed

between the centers of the lathe, and the

grinding attachment used in the ordinary

manner. If the lathe is not provided

with a grinding attachment, the emery

wheel may be mounted on an arbor

between the centers of the lathe. The Figs. 430 and 431. Typical whcda

for Grinding Gages

arbor may be driven from any accessible

pulley, either on some overhead countershaft or else on some machine

whose driving pulley is in line with a small pulley on the arbor. If

276

TOOL-MAKING

this method is used, it will be necessary to have hardened centers
in both head and tail spindles of the lathe.

A thin wheel used in grinding the surfaces of a narrow opening
necessitates that the tail center of the lathe be set over each way
to give the desired amount of clearance to the side of the emery wheel.
The holder mentioned may be fastened to the tool rest, or the gage

UW]

..S

>i'

-.-/-

I—

□

Fig. 432. Method of Fastening Gage for GriDding with Thin Whcela

may be fastened to the rest. Fig. 432. At the right is shown a side
view of one of the straps used to hold the work to the rest while
grinding; the center is represented as being cut away in order that
it may bear at its ends, thus removing any chance of its tipping the
work that is being ground.

Lapping Snap Gages, Where it is essential that gages retain
their exact size for a considerable length of time> the gaging surfaces

TOOL-MAKING

277

Fig. 438. Lap for OagiBC SurfMM

must be lapped to size after grinding. The surface left by the
emery wheel, even when the utmost care is used, consists of a series
of small ridges or irregularities which wear away as the gage is used

and leave the opening

too large. Lapping the C

gaging surfaces with oil

and emery grinds these

minute particles away and produces a perfectly flat surface, thereby

increasing the durability of the tool.

A convenient form of lap to use on snap gages is illustrated in
Fig. 433. It consists of a piece of copper or -brass wire, bent as
shown; the surface A is filed or hammered flat, and is charged with
some abrasive material, as emery. Extreme care must be used in
lapping the surfaces, that they may remain perfectly flat and parallel.
Unless the operator has had considerable experience in this particular
work, he wUl be likely to cut the edges away more than the center.
To avoid doing thb, pieces of hardened steel may be clamped to
each side of the gage before grinding. Fig. 434. As the tendency
when lapping is to make the outer edges round, the portions rounded

Fiit 434. Method of CUmpinc Pieoes on Gage to Prevent RoundiBg Edge*

will be the edges of the pieces clamped to the gage. After the gage
has been lapped to size these pieces may be removed.

Adjustable Snap Gage. Snap gages that are in constant use
soon wear to an extent that renders them useless, making it neoeaauy

2^8

TOOL-MAKING

to close them in, and grind and lap them to size agamror^else to
replace them with new ones. This tendency to wear, and the con-
sequent labor and cost of resizing or replacing, has caused the
adoption of. a style of snap gage whose size can be altered when
necessary; ihia form of gage is styled an adjustable snap gage.

The method of adjustment differs in different shops. Fig. 435
represents a form of adjustable snap gage which is not expensive
and which gives excellent results, because of the ease of- adjustment.
After blocking out the gage somewhere near to shape, the screw
hole for the adjusting screw C should be drilled and tapped, and the
slot milled for the adjustable jaw. The jaw should be made, as
shown, with a slot, through which the binding screw D may pass.
The jaw should- fit snugly in the sfot in*the frame, and be placed in

Q Q THICKNESS OF BREECH BLX)CK

1^9

Fig. 435. AdiuKable Snap Gage

position after the name and any distinguishing marks are stamped.
The aperture £ should be worked to a size that Is from .010 or .015
inch smaller than finish. The adjustable jaw B may then be removed,
and the gaging, or contact, surface hardened. Care should be taken
not to harden the entire length, or a crack may appear in the sharp
corners on account of the unequal size of the two parts. In order to
heat the contact surface and not to heat back into the sharp corners,
the face may be immersed in red-hot lead just long enough to heat the
face sufficiently; or the smaller portion may be held in a pair of
tongs, letting the end of the jaws come against the shoulders of the
piece. It may then be heateti in a gas jet or ordinary fire. For
most purposes it will be necfessary to harden the gage all over; if
the gaging portions A and B are hardened, this will be found

TOOL-MAKING

279

suffiticiit. After hardening, the gage may be assembled, ground,
and lopped, as Rlready explained.
Limit Qages. Where it is
not pecessary ttiat work be of
exact »2e, and a small degree
i^ variation is permissible, limit
gages are used, l^ey prevent a
waste of time in attempting
excessive aceuracy, yet leave the
work so that the correspondiiig
parts when brought together will
fit well enough to meet tequire-
meats. These gages are also val-
uable in roughing work for finish-
ing. When so used, practic^ly
the same amount of stock is
on each piece, thus facilitating
the finishing process.

If a cylindrical piece is
in a reamed hole, and the piece
fits well enough for all requirements when .003 inch smaller than
the size of the hole, it is (oily to spend the time necessary to get a
;tfit. Theai

B(TEflM*t

Fi(. <U. SUnpk Sq

of variation allowable must

bededdedineachcaseion

one job a limit ot variation

SVWVEL BOUT

of .001 inch might be all

that could be allowed, while

CSV

on another piece of work

SB9"

.010 inch might be allow-

<^~N

able.

1 f

In deciding the allow-

J I

able limit of variation, it

■i ?

is advisable, where possi-

1 1

ble, to take into considera- f., ij

PiM,

Finn. si»pCm<

take place ia the gage from wear.

Forir

stance, siippose a piece of

work .250 inch in diameter just fills the h

le for which it is designed,

280

TOOL-MAKING

and a limit of .0015 inch is allowable; if the piece is from .2485 inch
to .250 inch in diameter, it would be folly to make the large end of limit
gage for this work .250 inch, as there would be no allowance for
wear of either the external or internal gage. The general instructions
given for making plug gages and snap gages apply to limit gages
of the same character.

Illustratk>ns of Snap and Plug Limit Gages. Fig. 436 gives
an idea of one form of snap and plug gage used for external and
internal measurements; however, it is not necessary to make them
of the styles shown. The plug gage may be made as shown in

/•

■®^ '^

]o \

^ o

Fig. 439. pUgnun of Qua HaaoMr

Fig. 440. Receiving Gage for Gun Uanuiier

Fig. 437; while the snap gage may be made like the one illustrated
in Fig. 438.

Receiving Gages. When it is essential that the various working
points of a tool, part of a machine, or apparatus shall be in exact
relation to one or more given points, a receiving gage is used. This
gage, as the name implies, is made to receive, or take in, the work;
that is, the piece of work is placed in the gage, and the location
of the different points is determined by the eye.

Fig. 439 shows a gun hammer, while Fig. 440 represents a
receiving gage for accurately gaging the points C, D, E, F, G, and H,
in relation to the fulcrum screw hole A and the face B, These
points must also be in exact relation to each other — hence the

TOOL-MAKING 281

oecessity for a gage of this character. When making the gage,
it is customary in most shops to gage only those parts that must
be located accurately with relation to some other point or points.

Locating Poi/Us, In the case of the gun hammer under con-
sideration, the fulcrum screw hole A must be the main working
point, because when in use the gun hammer is pivoted at this
point, and, consequently, every point must be in exact relation
to this hole; the point of next importance is the face B which strikes
the firing pin. In order that the face of the hammer may be the
proper distance from the firing pin when half-cocked or full-cocked,
it is necessary that the half-cock notch Z), and the full-cock notch E
be. correctly located with regard to the face of the hammer. They
must also be in exact location as regards the fulcrum screw hole A.
If the main spring is to exert the proper amount of force on the
hammer, it is necessary that the spring seat G be Accurately located.
As the portions marked C and H are intended just to fill the opening,
in the gun frame when the hammer is in any position, it is necessary
that they be located the proper distance from the center of the
fulcrum screw hole A ; hence the need of a gage that will determine
the exact location of all points as related to A and B and to each
other. As the portions marked /, •/, K, L, Af , and N must be in
precise location to the other points or to each other, they are gaged
with a separate tool because each additional gaging point com-
plicates matters.

Making Base for Gage, When gages of this character are being
made, a piece of machine steel is usually taken for the base; this
is planed to size and ground or filed for finish ; a hole is drilled and
reamed to receive a pin the size of the fulcrum screw hole. This
pin is made of a piece of drill rod a few thousandths of an inch larger
than the desired pin. The piece of drill rod should be long enough
to be held in the chuck of the grinding machine, and should be cut
of the proper length, as shown in Pig. 441. The short end should
be hardened and the temper drawn to a straw color, after which
the pin may be placed in the chuck and ground to the desired size.
It may then be broken off and the end ground; this cian be done
by holding the pin in the chuck, leaving the broken end out in order
}hat it may be ground square; the pin should then be forced to place
in the hole ii\ the base.

282

TOOL-MAKING

Fig. 441 . BaM Pin tot Reociving Oage

Shaping Gage. The gage proper may be made of one plate
worked to the proper shape, but better results follow if it is made
in three pieces, as shown in Fig. 440, on account of the tendency of
the plate to spring when hardened. The plates may be made either

~^ of tool steel or machine steel.
If of tool steel, they should
be machined iall over and
thoroughly annealed, then
planed or milled to thick-
ness. One surface should be colored by the blue vitriol solution,
or the pieces may be heated until a distinct blue color appears;
the desired shape should be marked on the colored surface, and the
pieces machined and filed until they fit the model, the neeessary
degree of accuracy being determined by the nature of the work.
Fitting to Base, After the pieces are properly fitted to the
model, they may be attached to the base by means of the fillister
head cap screws shown. The model should be laid on the base
having the fulcrum screw hole on the pin, and when in its proper

Fig. Af2. Model of Gun HMnmer Clamped in PlAoe

location, it may be clamped, as shown in Fig. 442. The sections
of the gage, which should have been previously drilled for the screw
and dowel pins, may now be ckmped to the base in their proper
positions. After drilling, the holes in the base may be tapped,

TOOL-MAKING

283

and the screws put in place. Slight alterations in any of the shapes
are readily made if necessary, as the plates can be moved a trifle
since the bodies of the screws need not fit tightly in the holes in the
plates. The 'dowel pinholes should not be transferred into the oase
until after the plates are hardened.

Hardening. The plates may now be removed and hardened.
If of machine steel, they may be casehardened, and dipped in oil
rather than water. If made of tool steel, best results follow if
they are pack hardened; they should be run from 1 hour to IJ hours
after becoming red hot, and then dipped in raw linseed orl. If the
process of pack hardening cannot be used, satisfactory results may
be obtained by heating the plates in a tube in an open fire, or placed
in the muffie of a muffle furnace. When red hot sprinkle a small

Fig 443. Locating Gage

Fig. 444. Piece with Hole
to Be T.x>«ated

quantity of finely powdered cyanide of potassium, or a little yellow
prussiate of potash, on the contact surface; place it in the fire again;
bring it to a low red heat, and plunge it into a bath of oil.

Attacking to Base. After being hardened, the plates may be
attached to the base by means of the screws. If any of the gaging
points have become distorted during the hardening, they may be
brought to the proper shape by oil-stoning. When the plates are
j:>roperly fitted and located in their exact positions, the dowel pin
holes may be transferred into the base and the dowel pins put
in place.

Locating Qages. This f6rm of gage is used for determining
the location of one or more holes in relation to another hole, a
shoulder, a working surface, or any similar measurement.

Fig. '143 illustrates a gage for showing the proper location of
the hole from the edges A and B^ Fig. 444. It consists of a base

3S4

TOOL-MAKING

having four pins for the edges A and B to rest against. These
[nns are flatted on the contact edges to prevent wearing. The
laece of work to be gaged is placed in position and clamped to the
gage with niachiniat'a clamps, Fig. 446, and the gage is fastened
to the laceplate of the
lathe in such a manner
that the work can be
removed without dis-
turbing the location of
the gage

A short plug, fitting
very acturately, is then
inserted in the hole in
the model. 6)' n)eun»
of a Jathe indicator the
gage can be located so
that the plug runs per-
fectly true. When thb has been accomplished, the model may be
removed and the bushing hole drilled and bored to size, after which
the bushing may be made, hardened, ground to size, and forced to
place. The location of the drilled hole may be tested by placing
the piece of work on the gage against the pins, and entering (he
- gage pin in the hole in the work

and bushing, Fig. 446. If the pin
is a close lit in the holes, a very
slight error in location may be
detected. When a slight error is
allowable, and it is not considered
advisable to hold the location too
dose, the pin may be made a trifle
small, thus transforming the gage
info a limit gage.
F«. M« Ofi^t Hole " ■<■ 's necessary to make a

locating gage, for testing the center
distance of two holes, one pin may be made t«movable, while the
other is rigidly fixed, as shown at C, Fig. 447. If the.gage ia made
with both pins fixed, and the pins are a good fit in the holes, it isa
difficult oper^dn to refnove the piece of work. Withdrawing

TOOL-MAKING

285

^ §

one pin allows t)ie piece of work to be readily taken from the

fixed pin.

When making a gage of the form shown in Fig,. 447, the fixed
pin C may be located by approximate measurements; but the hole
should be drilled by some
method that insures the pin
standing perfectly square
with the base of the gage.
If a small limit of variation
is permissible in the center
to center measurement Ay
the model may be placed
on the gage with the large
hole on the fixed pin C, and
the location of the hole for
the movable pin may be
transferred from the model
by drilling and reaming.
If extreme accuracy is essen-
tial, it will be advisable to
clamp* the model to- the
gage as described, then to fasten the gage to the faceplate of the
lathe, place an accurately fitting pin in the small hole in the model,
and by means of a lathe indicator locate the gage so that the pin

Fi«. 447 Simple Form of Locating Gage
Showing Method of Vse

Fig. 44&. Gage for Measuring Locations and Directions of Holes,

^uns perfectly true. The model may then be removed and the hole
drilled and bored to size.

Locating gages are made to measure the location of one or
more holes from another hole or shoulder, or both. Fig. 448 is a
gage to measure the locations of holes a and 6 from the hole c and

286

TOOL-MAKING

Pig. 440. Micrometer Gage

'shoulder d. The hole e is set on a iitud solid with the base, and a
and b are gaged by means of the hardened and ground pins shown.

Micrometer Gage,
Micrometer locating
gages are very commonly
used in many shops. '
, They are especially valu-
able for measuring such
pieces as require very
close watching, or where
a certain variation is
permissible, for by means
of micrometer readings
the amount of variation
in thousandths of an inch is easily determined. Fig. 449 shows a
micrometer gage used in measuring the angle surface a in connec-
tion with base b and shoulder c,

DRAW-IN CHUCKS

In many shops, the bench lathe plays a very important part
in the making of all kinds of small tools. The lathes, being pro-
vided with draw-in chucks, allow the extensive use of drill rod
when majcing reamers, counterbores, milling cutters, punches to
be used in the punch press, and many other forms of tools. As the
modem tool room bench lathe has a milling attachment and a grind-
ing head, it is possible to turn up various forms of tools, and then to
do such milling and grinding as is necessary.

While a lathe is usually equipped with an assortment of draw-in
chucks to hold stock of various sizes, it is necessary many times
to replace a chuck or to make one of special size to accommodate
a job that cannot be done in any chuck on hand.

Directk>ns for Making. The methods employed in- various
shops for making draw-in chucks differ materially, but the following
method will be found very satisfactory and does not necessitate
special tools:

A piece of tool steel somewhat larger than the largest portion
of finished chuck is cut off fron\ ^ inch to i inch longer than the
finish dimension.. After centering, the _ends should be carefully

TOOL-MAKING

287

Fie. 450. Draw-In Chuek Blank

squared and a roughing chip taken. The lafge clearance hole
should now be drilled by holding the end F, Fig. 450, in a center
rest, and using a drill held in a chuck in the tail .spindle of the lathe.
Before removing the piece
from the center rest, care-
fully countersink the outer
end of the hole with a suit-
able tool to an angle of GO
degrees.

The piece is now placed
between the centers of a lathe, the portions B, D, E, and f turned
to finish size, and the thread at F cut to fit the threaded hole in
the draw-in spindle. The portion C is left a little large to allow
for grinding after the chuck is hardened.

The portion A is turned, as shown, to provide a center for use
in turning and grinding; it also holds the chuck in shape when it
is hardened as the slots do not extend the length of this portion.
The spline cut to receive the feather in the spindle is now milled,
the piece being held between the centers of the index
head. After the burrs have been removed the piece is
inserted in the lathe spindle, and the hole to receive
the work is drilled and reamed to a size enough
smaller than finish siz>e to allow for grinding after the
chuck is hardened.

The piece is again placed between the index '~ "'■»■• ^""
centers and the three slots cut, Fig. 451 . As previously stated, these
slots should not extend through the portion A, Fig. 450, but should
be as shown in Fig. 451, and should clea( the hole. The slots should
extend into portion E, Fig. 450, a little way. The
metal slitting saw used in producing the slots should
be of as small diameter as can be conveniently
used, and should not be too thick, as a thick cutter
would, in the case of a chuck with a small hole, cut
away all the hole. For chucks with large holes, a
slot as shown jn Fig. 451 works well; but, for
chucks with small holes a comparatively thick saw may be used
to cut the slot nearly to depth; then a thin cutter may be substi-
tuted to finish it as shown in Fig. 452. Before, hardening, the

Fig. 451. End
of Draw-In Chuck

Fig. 452. End
of Draw-In Chuek
for Smntt Drilli

288 TOOL-MAKING

siie ot the finish hole should be stamped on the face of the chuck.
A 'finished chuck tA this type is ahown in Fig. 453.

An oven furnace provides an excellent means of heeting for
hardening. If an open fire must be used, the chuck should be placed
in a piece of gas pipe, heated to a uniforni low red, and plunged into
a bath of lukewarm water or brine a littl^ above the ends of the
slots. The temper of the portions B and C, Fig. 450, should then
be drawn to a brown, and the rest of the hardened part to a blue.

The chuck should now be placed between the centers of a
universal grinder, or,, in the absence of such a machine, in a grinding

lathe, and the portion C ground to finish size and to fit the taper
in the nose of the lathe spindle; If many chucks are made, it is
advisable to grind to a gage; but, where there are only one or two,
it is not necessary to go to the expense of a special gage.

After the portion C has been ground to fit, the chuck may be
mserted in the spindle of the lathe, the hole ground to size, tho
portion A ground away, and the face polished. The chuck is now
ready, for use.

INDEX.

2 INDEX

PAGE

Bushings 186

bushings, removable 188

drill jigs, for 167, 186

punch guide 216

Carbon steel, high- and low- 11, 248

Casehardening 23

bone and charcoal, use of 24

machine-steel plug gage, of 265

potassium cyanide, use of ^ 23

melted 26

Cast iron as tool material 8

Cemented steel in tool-making 9

Chambering reamer 60

Chucking reamer, fluted 49

Citric-acid bath for hardening 20

Cold-striking dies 262

Combination counterbore - 1 13

Compound dies 225, 230

Converted steel in tool-making 9

blister steel 9

cementation process 9

shear steel 9

Cored-hole drill jig 183

Counterbores 103

adjustable-cutter type, single-edged 112

combination 113

facing tool, inserted-cutter 107

flat, two-edged 103

four-edged, common 104

inserted-pilot type, making 109

large-work type, making 107

making, general process of 104

special 106

Crucible steel in tool-making 10, 1 1

cast steel 10

hardening and tempering of 18

preparation of 11

Curling die 228

Cyaniding 23, 26

Deep-hole drill 42

Die block 193

Die-filing machine 199

Die holder 195

for thread-cutting dies 07, 102

Die-maker's square 6

INDEX 3

PAGE

Die-sinking 197

Dies, types of 193

bending ' 218

compound 225, 230

curling 228

drop-forging 254

fluid 237

follow : 226

forming 221

gang 213

multiple 217. 225

piercing-and-curling . , 212

progressive 231

reversed '. 224

sectional 202

sub-press 234

thread-cutting 93

wiring 229

Draw-in chuck, making 286

Drill jigs 164, 185

box type 189

bushing of » 167. 186

cored-hole 183

fastening devices ^ 185

rotating type 191

slab type, simple 166

supported type 179

rapid-operating 180

Drills, types of 32

flat 32

straightway fluted 34

single-lip 35

special 42, 44

twist ■ 38

Drop-forging dies 254

cold-striking 262

making ' 257

bobbing process 261

process of using 255

breaking-down 255

machines for 255

trimming of flash ^ . . . . 257

Drop-forging process 255

Eccentric arbor 69

End mill 152

center-cut type 154

spiral form 154

4 INDEX

PAGE

Equipment of tool-maker 1

requirements, fundamental 1

tools and appliances, neoeesary 4

angle ffages 5

blue-vitriol solution » 6

die-maker's square 6

straightedges 6

surface-gage scale attachment 4

Y-blocks 6

vernier caliper 2

vernier height ga^e 4

Expanding mandrels 67

Face milling cutter 156

Facing tool, inserted-cutter oounter-horing 109

Fastening devices for jigs 185

Flash, drop forging 257

Flat oounterbore, two-edged 103

Flat drill 32

transfer type of »33

Fluid die 237

Flutes for counterbores 104

Flutes for hand and chucking reamprs 46, 49

Flutes for rose reamers 52

Flutes for straightway drills 34

Flutes for tape 76

Flutes for twist drills , . . . 38

Fly cutter 151

FoUow die 226

Formed milling cutters 143

Formed reamers 60

Forming die 221

Forming tools 119

high-speed steel 125

holders for 124

screw-machine types 121

Gages, typeB and design of 263

limit 279

locating 283

making, accuracy in 264

micrometer 286

plug 265, 280

receiving, making of 280

ring 268

snap 271. 280

Gang die 213

INDEX &

PAGE

Grinding hand taps 80

Grinding plug gages 266

Grinding ring gages 269

Grinding snap gages 274

Grinding straight reamer 48

Grinding twist drills 42

Hammered steel 11

Hand reamer, fluted 46

Hand taps. . .' 76

Hardening 15, 18

broaches, of 251

casehardening process 23

dtric-acid bath, with 21

cooling operation 19

dies, -of > 204, 223, 236

heating operation 19

high-speed steel dies, of 236

mandrels, of 64

oil bath, use erf 23

pack-hardening process 21

punches, of 208

reamers, of 47, 62

receiving gage, of 283

taps, of 79

twist drills, of 41

variations for high-speed steel tools « 28

High-speed steel 28

• annealing of '. 30

dies 236

drills 44

forging of 28

forming tools 126

hardening, variation in 28

merits of 31

milling cutter. 126

pack hardening of 30

tempering of 30

Hobbing drop-forging dies 261

Hobs for screw dies 81

Holder for reamer 62

Holder, releasing tap 90

Holder, special, for milling machine 163

Hollow mills 114

adjustable type 116

inserted-blade type .117

pilot type 118

Hollow punch 238

6 INDEX

I PAOB

Inserted-blade hollow mill 117

Inserted-blade reamer 54

Inserted-blade tap 84

Inserted-pilot counterborc 109

Inserted-tooth milling cutter 139

Interlooldng-tooth milling cutter 136

Iron in tool-making 8

cast • 8

wrought 8

Jam die plate 73

Keyseating machine for broaching 253

Keyways, milling-cutter 142

standard dimensions 142

Lap 266

Lapping of plug gage .' 266

Lapping of snap gage 276

Limit gage 279

Locating gage * 283

Machine steel in tool-making 8

Bessemer type 8

casehardening, for plug gage 265

mandrels of 67

open-hearth type 8

Machine tap 80

Machines, care of 3

Mandrels 63

expanding 67

hardened-end type 67

machine-steel 67

sises, table of 65

tool-steel 63

grinding of 66

hardening of 64

lapping of 66

tapering of » 67

Materials for tool-making 8

cast iron 8

converted steel 9

crucible steel 10

high-speed steel 28

machine steel 8

wrought iron 8

INDEX 7

PAGE

Micrometer gages 286

Milling cutters 126

cutting edges for 127

end mills 152

face type 156

arbor for 158

sises, table of 157

fly-cutter t3rpe 151

formed type 143

backing off 144

high-speed steel 126

inserted-tooth type 139

interlocking-teeth 136

keywasrs for 141

slotting type, split 137

solid type 127

angular faced 139

nicked teeth 135

saws, metal-slitting 128

side-cutting 132

spiral teeth 134

threaded 149

T-filot type 156

Milling-machine fixtures 158

arbors 71

cam 161

continuous-process 164

essentials of . . . .! 159

holders, special 163

screw 1 161

vises 160

compressed-air operated 161

special jaw 161

wedge key 163

Multiple die 217. 225

N
Nicked teeth 135

Oil-hardening steels as tool material ' 27

Open-hearth process machine steel 8

Pack-hardening 21

high-speed steel 30

Pilot for hollow mill 118

Plug gage 265, 280

casehardening of machine-steel 265

8 INDEX

Plug gage (continued) paqe

grinding of 266

lapping of 266

Plug tap 76

Punch 193

Punch-and-die work 193

die 193

block 193

holder for 195

stripper 194, 210

typee of 202,

212. 213, 217. 218. 221. 234. 225, 226, 228, 229. 230. 231. 234. 237

die-making 196

filing 198

hardening 204, 223, 236

high-speed steel, use of 236

repairing 215

shearing-in 200. 207

sinking, milling or ' 197

tempering 205

punch 193, 206

biishing for, guide 216

hardening of 208

hollow type 238

machining of 207

spreading type 217

Push broaches 253

Pyrometers 15

clay sentinel cones, use of 17

Rake of die thread-cutting edges 94

Reamers 45

formed 60

chambering type 60

hardening of 62

square 61

holder for 62

straight 45

adjustable 55

fluted chucking type 49

fluted hand type 46

grinding of 48

hardening of 47

inserted-blade 54

rose 60

roughing, three-and four-lipped 53

shell 56

single-lip 52

straighteninit of 48

INDEX 9

Reamers (continued) paqe

tapered 59

roughing type 59

Receiving gi«e , . 280

Repairing of die 215

Ring gage 268

Roee reamer 50

Rotating jigs. 191

Roughing reamers 53, 59

S .

Saw, metal-slitting 128

Screw-machine forming tools 121

Sectional die 202

Shear steel in tool-making 9

Shearing of punch and die 200, 207

Shell reamer 56

arbor for 58

Side milling cutter 132

Single-lip drUl 35

inserted-cutter type 36

Single-lip reamer. 52

Sixing die for tape 73

Slab jig 166

Slotting milling cutter, split 137

Snap gage 271, 280

adjustable type 277

cylindrical work, for 272

grinding of 274

lapping of 276

male gage for testing 273

Spiral end mill 154

Spiral milling cutter 134

nicked-tooth 135

Spreading punch 217

Spring tempering 23

Spring thread-cutting dies 99

Square reamer 61

Steel in tool-making 8

alloy 26

Bessemer 8

broach 247

carbon tool, high- and low- 11

crucible tool, treatment of 11

distinguishing kinds of 31

hardening of 15, 18

high-speed 28

oil-hardening type 27

open-hearth 8

tap 75, 89

10 INDEX

Steel in tool-nialdnc (continued) page

tempering of 18, 22

tungsten, self-hardening 27

Straightedges 6

Straightening of reamers 48

Straightoung of tool steel 12

Straightway fluted drill 34

Stripper 194, 210

Sub-press die 234

Supported jigs 179

Surface-gage scale attachment 6

T
Tables

dies, ^ring screw-threading 100

mandrels, dimensions, to 1-inoh 65

milling cutters, cutting edges of 127

milling cutters, data for face-type 157

milling cutters, standard keyways for 142

shell reamers, dimensions of 56

temper, color indication of. 23

twist drills, data for cutting 39

Tap wrench 89

Taper tap 75

Taps 73

adjustable 82

hand type 76

fluting of 76

grinding of 80

hardening of 79

holder for, releasing 90

inserted-blade type 84

machine type 80

screw dies for 73

hobs for 81

sets 75

bottoming tap ^ 76

taper tap 75, 81

plug tap 76

steel for 75, 89

threads of 86

formulas for 86

left-hand 88

square 87

wrenches for 89

Tempering 18, 22

ecioT indication in 23

dies, of 205

thread-cutting type 98

high-speed steel tools 31

springs, treatment of 23

taps, of 86

INDEX 11

PAOK

Thread-cutting dies 93

adjustable type 96

adjustment method^ 96

heat-treating of 98

. holders for 97, 102

machining of 98

sises for spdng screw-threading dies 100

spring form 99

tap making 73

solid type 93

circular shaped 96

clearance holes 95

cutting edges 94

machining process 93, 94

Threaded milling cutter 149

Threads^ formulas for tap 86

Tool holders for forming tools 124

Tool-making 1-288

arbors 63

broaches 241

chucks, draw-in 286

counterbores 103

driU jigs 164, 186

drills 32

drop-forging dies 254

equipment 1

forming tools 119

gages 263

hollow mills 114

materials, treatment of 8

milling cutters 126

milling-machine fixtures 158

punch-and-die work 193

reamers 45

taps 73

thread-cutting dies 93

Tool steel, treatment of crucible 11

annealing 13

hardening 15, 18

pyrometer, use of i, 15

stock for 11

carbonisation of 11

centering of 12

cutting off of 12

hammering of 11

straightening of 12

tempering 18, 22

Transfer drill 33

Trimming operation 257

T-slot milling cutter 155

12 INDEX

PAGE

Twist drills 38

bacldng off , 40

cutting, data for 39

deep-hole type 42

grinding 42

hardening 41

high-^peed steel for 44

milling flutes in 38

rapid operating types 45

V-blocks 5

Vernier caliper, use of 2

Vernier height gage 4

Vise, milling-machine 160

compressed-air type 161

Wrought iron m tool material 8

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Full text of "Tool making; a practical treatise on the art of making tools, jigs, and fixtures, with helpful suggestions on heat treatment of carbon and high-speed steels for tools, punches, and dies"

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